diff --git a/bench-micro/.gitignore b/bench-micro/.gitignore
new file mode 100644
index 000000000000..1a06816d838d
--- /dev/null
+++ b/bench-micro/.gitignore
@@ -0,0 +1 @@
+results
diff --git a/bench-micro/scripts/run.sh b/bench-micro/scripts/run.sh
new file mode 100755
index 000000000000..06b2445d2391
--- /dev/null
+++ b/bench-micro/scripts/run.sh
@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+
+name=$1
+runs=2
+
+run_benchmark() {
+    jvm=$1
+    jvm_coursier_id=$2
+    run=$3
+    json_file=results/$name-$jvm-$run.json
+    txt_file=results/$name-$jvm-$run.txt
+
+    eval "$(coursier java --jvm "$jvm_coursier_id" --env)"
+    rm -rf "$json_file" "$stdout_file" .bloop .sbt .bsp .metals target
+    sbt "clean; scala3-bench-micro / Jmh / run -rf JSON -rff $json_file -o $txt_file $name"
+}
+
+for run in $(seq 1 $runs); do
+    run_benchmark openjdk "adoptium:1.17.0.11" $run
+    run_benchmark graal "graalvm-java17:22.3.3" $run
+done
diff --git a/bench-micro/src/main/scala/dotty/tools/benchmarks/AnnotationsMappingBenchmark.scala b/bench-micro/src/main/scala/dotty/tools/benchmarks/AnnotationsMappingBenchmark.scala
new file mode 100644
index 000000000000..dd2967790454
--- /dev/null
+++ b/bench-micro/src/main/scala/dotty/tools/benchmarks/AnnotationsMappingBenchmark.scala
@@ -0,0 +1,221 @@
+package dotty.tools.benchmarks
+
+import org.openjdk.jmh.annotations.{Benchmark, BenchmarkMode, Fork, Level, Measurement, Mode as JMHMode, Param, Scope, Setup, State, Warmup}
+import java.util.concurrent.TimeUnit.SECONDS
+
+import dotty.tools.dotc.{Driver, Run, Compiler}
+import dotty.tools.dotc.ast.{tpd, TreeTypeMap}, tpd.{Apply, Block, Tree, TreeAccumulator, TypeApply}
+import dotty.tools.dotc.core.Annotations.{Annotation, ConcreteAnnotation, EmptyAnnotation}
+import dotty.tools.dotc.core.Contexts.{ContextBase, Context, ctx, withMode}
+import dotty.tools.dotc.core.Mode
+import dotty.tools.dotc.core.Phases.Phase
+import dotty.tools.dotc.core.Symbols.{defn, mapSymbols, Symbol}
+import dotty.tools.dotc.core.Types.{AnnotatedType, NoType, SkolemType, TermRef, Type, TypeMap}
+import dotty.tools.dotc.parsing.Parser
+import dotty.tools.dotc.typer.TyperPhase
+
+/** Benchmark to compare different ways to map concrete annotations.
+  *
+  * The main performance bottleneck there is the mapping of the annotation's
+  * inner tree of; a `TreeTypeMap` is much slower than a `TypeMap`.
+  *
+  * Run with: scala3-bench-micro / Jmh / run AnnotationsMappingBenchmark
+  */
+@Fork(value = 5)
+// Set to 0 to record all iterations. We remove the first iterations manually
+// when processing the results.
+@Warmup(iterations = 0, time = 1, timeUnit = SECONDS)
+@Measurement(iterations = 10, time = 1, timeUnit = SECONDS)
+@BenchmarkMode(Array(JMHMode.Throughput))
+@State(Scope.Thread)
+class AnnotationsMappingBenchmark:
+  var tp: Type = null
+  var specialIntTp: Type = null
+  var context: Context = null
+  var typeFunction: Context ?=> Type => Type = null
+  var typeMap: TypeMap = null
+
+  @Param(Array("v1", "v2", "v3", "v4"))
+  var valName: String = null
+
+  @Param(Array("current", "oldCheck", "newCheckEquals", "newCheckEq", "noCheck", "noCheckCopySymbols"))
+  var typeMapName: String = null
+
+  @Param(Array("id", "mapInts"))
+  var typeFunctionName: String = null
+
+  @Setup(Level.Iteration)
+  def setup(): Unit =
+    /** A custom phase that is used to retrieve the `Type`s and `Context` to be
+      * used in the benchmark.
+      */
+    val testPhase =
+      new Phase:
+        final override def phaseName = "testPhase"
+        final override def run(using ctx: Context): Unit =
+          val pkg = ctx.compilationUnit.tpdTree.symbol
+          tp = pkg.requiredClass("Test").requiredValueRef(valName).underlying
+          specialIntTp = pkg.requiredClass("Test").requiredType("SpecialInt").typeRef
+          context = ctx
+
+    /** A custom compiler that only runs the `Parser`, `TyperPhase` and
+      * `testPhase`.
+      */
+    val compiler =
+      new Compiler:
+        private final val baseCompiler = new Compiler()
+        final override def phases = List(List(Parser()), List(TyperPhase()), List(testPhase))
+
+    /** A custom driver that uses `compiler`. */
+    val driver =
+      new Driver:
+        final override def newCompiler(using Context): Compiler = compiler
+
+    // Runs the driver with the test file.
+    driver.process(Array("-classpath", System.getProperty("BENCH_CLASS_PATH"), "tests/someAnnotatedTypes.scala"))
+
+    typeFunction =
+      typeFunctionName match
+        case "id"      => tp => tp
+        case "mapInts" => tp => (if tp frozen_=:= defn.IntType then specialIntTp else tp)
+        case _         => throw new IllegalArgumentException(s"Unknown type function: $typeFunctionName")
+
+    /** Creates a new `TypeMap` that uses `mapConcreteAnnotationWith` to map
+      * concrete annotations. It is used to compare several ways to map these
+      * annotations.
+      */
+    def makeTypeMap(mapConcreteAnnotationWith: (ConcreteAnnotation, TypeMap) => Context ?=> Annotation) =
+      new TypeMap(using context):
+        final override def apply(tp: Type): Type = typeFunction(mapOver(tp))
+        final override def mapOver(tp: Type) =
+          tp match
+            case tp @ AnnotatedType(underlying, annot) =>
+              val underlying1 = this(underlying)
+              val annot1 =
+                annot match
+                  case annot: ConcreteAnnotation => mapConcreteAnnotationWith(annot, this)
+                  case _                         => annot.mapWith(this)
+              if annot1 eq EmptyAnnotation then underlying1
+              else derivedAnnotatedType(tp, underlying1, annot1)
+            case _ => super.mapOver(tp)
+
+    /** Retrieves all argument from a tree. This old implementation does not
+      * include type arguments.
+      */
+    def oldAllArguments(tree: Tree)(using Context): List[Tree] =
+      tpd.unsplice(tree) match
+        case Apply(fn, args)  => oldAllArguments(fn) ::: args
+        case TypeApply(fn, _) => oldAllArguments(fn)
+        case Block(_, expr)   => oldAllArguments(expr)
+        case _                => Nil
+
+    /** This is the old (<= d1489734b7) implementation of `Annotation.mapWith`.
+      * It 1. does not include type arguments and 2. uses `frozen_=:=` to
+      * compare types and 3. does not copy all symbols.
+      */
+    def oldMapWith(annot: ConcreteAnnotation, tm: TypeMap)(using Context): Annotation =
+      val tree = annot.tree
+      val args = oldAllArguments(tree)
+      if args.isEmpty then annot
+      else
+        val findDiff = new TreeAccumulator[Type]:
+          def apply(x: Type, tree: Tree)(using Context): Type =
+            if tm.isRange(x) then x
+            else
+              val tp1 = tm(tree.tpe)
+              foldOver(if tp1 frozen_=:= tree.tpe then x else tp1, tree)
+        val diff = findDiff(NoType, args)
+        if tm.isRange(diff) then EmptyAnnotation
+        else if diff.exists then annot.derivedAnnotation(tm.mapOver(tree))
+        else annot
+
+    /** Retrieves all argument from a tree, including type arguments. */
+    def newAllArguments(tree: Tree)(using Context): List[Tree] =
+      tpd.unsplice(tree) match
+        case Apply(fn, args)     => newAllArguments(fn) ::: args
+        case TypeApply(fn, args) => newAllArguments(fn) ::: args
+        case Block(_, expr)      => newAllArguments(expr)
+        case _                   => Nil
+
+    /** This is the new implementation of `Annotation.mapWith`. It 1. includes
+      * type arguments and 2. uses `==` to compare types and 3. copies all
+      * symbols by using a custom `TreeTypeMap` that overrides `withMappedSyms`.
+      */
+    def newMapWithEquals(annot: ConcreteAnnotation, tm: TypeMap)(using Context): Annotation =
+      val tree = annot.tree
+      val args = newAllArguments(tree)
+      if args.isEmpty then annot
+      else
+        val findDiff = new TreeAccumulator[Type]:
+          def apply(x: Type, tree: Tree)(using Context): Type =
+            if tm.isRange(x) then x
+            else
+              val tp1 = tm(tree.tpe)
+              foldOver(if tp1 == tree.tpe then x else tp1, tree)
+        val diff = findDiff(NoType, args)
+        if tm.isRange(diff) then EmptyAnnotation
+        else if diff.exists then
+          val ttm =
+            new TreeTypeMap(tm):
+              final override def withMappedSyms(syms: List[Symbol]): TreeTypeMap =
+                withMappedSyms(syms, mapSymbols(syms, this, mapAlways = true))
+          annot.derivedAnnotation(ttm.transform(tree))
+        else annot
+
+    /** Exactly the same as `newMapWithEquals`, but uses `eq` instead of `==` to
+      * compare types.
+      */
+    def newMapWithEq(annot: ConcreteAnnotation, tm: TypeMap)(using Context): Annotation =
+      val tree = annot.tree
+      val args = newAllArguments(tree)
+      if args.isEmpty then annot
+      else
+        val findDiff = new TreeAccumulator[Type]:
+          def apply(x: Type, tree: Tree)(using Context): Type =
+            if tm.isRange(x) then x
+            else
+              val tp1 = tm(tree.tpe)
+              foldOver(if tp1 eq tree.tpe then x else tp1, tree)
+        val diff = findDiff(NoType, args)
+        if tm.isRange(diff) then EmptyAnnotation
+        else if diff.exists then
+          val ttm =
+            new TreeTypeMap(tm):
+              final override def withMappedSyms(syms: List[Symbol]): TreeTypeMap =
+                withMappedSyms(syms, mapSymbols(syms, this, mapAlways = true))
+          annot.derivedAnnotation(ttm.transform(tree))
+        else annot
+
+    def noCheckMapWith(annot: ConcreteAnnotation, tm: TypeMap)(using Context): Annotation =
+      annot.derivedAnnotation(tm.mapOver(annot.tree))
+
+    def noCheckCopySymbolsMapWith(annot: ConcreteAnnotation, tm: TypeMap)(using Context): Annotation =
+      val ttm =
+        new TreeTypeMap(tm):
+          final override def withMappedSyms(syms: List[Symbol]): TreeTypeMap =
+            withMappedSyms(syms, mapSymbols(syms, this, mapAlways = true))
+      annot.derivedAnnotation(ttm.transform(annot.tree))
+
+    typeMap =
+      typeMapName match
+        case "current" =>
+          new TypeMap(using context):
+            final override def apply(tp: Type): Type = typeFunction(mapOver(tp))
+        case "oldCheck" =>
+          makeTypeMap(oldMapWith)
+        case "newCheckEquals" =>
+          // This should be the same as `current`, modulo a few indirections.
+          makeTypeMap(newMapWithEq)
+        case "newCheckEq" =>
+          makeTypeMap(newMapWithEq)
+        case "noCheck" =>
+          makeTypeMap(noCheckMapWith)
+        case "noCheckCopySymbols" =>
+          makeTypeMap(noCheckCopySymbolsMapWith)
+        case _ =>
+          throw new IllegalArgumentException(s"Unknown type map: $typeMapName")
+
+  @Benchmark
+  def applyTypeMap() =
+    val res = typeMap.apply(tp)
+    // println(res.show(using context))
diff --git a/bench-micro/tests/someAnnotatedTypes.scala b/bench-micro/tests/someAnnotatedTypes.scala
new file mode 100644
index 000000000000..8b12d4f7c2c6
--- /dev/null
+++ b/bench-micro/tests/someAnnotatedTypes.scala
@@ -0,0 +1,28 @@
+class Test:
+  class FlagAnnot extends annotation.StaticAnnotation
+  class StringAnnot(val s: String) extends annotation.StaticAnnotation
+  class LambdaAnnot(val f: Int => Boolean) extends annotation.StaticAnnotation
+
+  type SpecialInt <: Int
+
+  val v1: Int @FlagAnnot = 42
+
+  val v2: Int @StringAnnot("hello") = 42
+
+  val v3: Int @LambdaAnnot(it => it == 42) = 42
+
+  val v4: Int @LambdaAnnot(it => {
+    def g(x: Int, y: Int) = x - y + 5
+    g(it, 7) * 2 == 80
+  }) = 42
+
+  /*val v5: Int @LambdaAnnot(it => {
+    class Foo(x: Int):
+      def xPlus10 = x + 10
+      def xPlus20 = x + 20
+      def xPlus(y: Int) = x + y
+    val foo = Foo(it)
+    foo.xPlus10 - foo.xPlus20 + foo.xPlus(30) == 62
+  }) = 42*/
+
+  def main(args: Array[String]): Unit = ???