diff --git a/python/src/com/jetbrains/python/codeInsight/imports/PyImportOptimizer.java b/python/src/com/jetbrains/python/codeInsight/imports/PyImportOptimizer.java
index 169fe306bfaf..a4e9ca4abb24 100644
--- a/python/src/com/jetbrains/python/codeInsight/imports/PyImportOptimizer.java
+++ b/python/src/com/jetbrains/python/codeInsight/imports/PyImportOptimizer.java
@@ -19,6 +19,7 @@ import com.google.common.collect.Ordering;
 import com.intellij.codeInspection.LocalInspectionToolSession;
 import com.intellij.lang.ImportOptimizer;
 import com.intellij.openapi.util.Condition;
+import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiFile;
 import com.intellij.util.containers.ContainerUtil;
 import com.jetbrains.python.codeInsight.imports.AddImportHelper.ImportPriority;
@@ -49,8 +50,8 @@ public class PyImportOptimizer implements ImportOptimizer {
                                                                                                           Collections.<String>emptyList());
     file.accept(new PyRecursiveElementVisitor() {
       @Override
-      public void visitPyElement(PyElement node) {
-        super.visitPyElement(node);
+      public void visitElement(PsiElement node) {
+        super.visitElement(node);
         node.accept(visitor);
       }
     });
diff --git a/python/src/com/jetbrains/python/inspections/unresolvedReference/PyUnresolvedReferencesInspection.java b/python/src/com/jetbrains/python/inspections/unresolvedReference/PyUnresolvedReferencesInspection.java
index be33d6f0eeb9..b80cfa0ecdde 100644
--- a/python/src/com/jetbrains/python/inspections/unresolvedReference/PyUnresolvedReferencesInspection.java
+++ b/python/src/com/jetbrains/python/inspections/unresolvedReference/PyUnresolvedReferencesInspection.java
@@ -42,6 +42,7 @@ import com.jetbrains.python.PyCustomType;
 import com.jetbrains.python.PyNames;
 import com.jetbrains.python.codeInsight.PyCodeInsightSettings;
 import com.jetbrains.python.codeInsight.PyCustomMember;
+import com.jetbrains.python.codeInsight.PyFunctionTypeCommentReferenceContributor;
 import com.jetbrains.python.codeInsight.controlflow.ScopeOwner;
 import com.jetbrains.python.codeInsight.dataflow.scope.ScopeUtil;
 import com.jetbrains.python.codeInsight.imports.AutoImportHintAction;
@@ -286,6 +287,13 @@ public class PyUnresolvedReferencesInspection extends PyInspection {
       if (comment instanceof PsiLanguageInjectionHost) {
         processInjection((PsiLanguageInjectionHost)comment);
       }
+      if (PyFunctionTypeCommentReferenceContributor.TYPE_COMMENT_PATTERN.accepts(comment)) {
+        for (PsiReference reference : comment.getReferences()) {
+          if (reference instanceof PsiPolyVariantReference) {
+            markTargetImportsAsUsed((PsiPolyVariantReference)reference);
+          }
+        }
+      }
     }
 
     @Override
@@ -323,15 +331,7 @@ public class PyUnresolvedReferencesInspection extends PyInspection {
               if (element instanceof PyReferenceOwner) {
                 final PyResolveContext resolveContext = PyResolveContext.noImplicits().withTypeEvalContext(myTypeEvalContext);
                 final PsiPolyVariantReference reference = ((PyReferenceOwner)element).getReference(resolveContext);
-                final ResolveResult[] resolveResults = reference.multiResolve(false);
-                for (ResolveResult resolveResult : resolveResults) {
-                  if (resolveResult instanceof ImportedResolveResult) {
-                    final PyImportedNameDefiner definer = ((ImportedResolveResult)resolveResult).getDefiner();
-                    if (definer != null) {
-                      myUsedImports.add(definer);
-                    }
-                  }
-                }
+                markTargetImportsAsUsed(reference);
               }
             }
           }.visitElement(pair.getFirst());
@@ -339,6 +339,18 @@ public class PyUnresolvedReferencesInspection extends PyInspection {
       }
     }
 
+    private void markTargetImportsAsUsed(@NotNull PsiPolyVariantReference reference) {
+      final ResolveResult[] resolveResults = reference.multiResolve(false);
+      for (ResolveResult resolveResult : resolveResults) {
+        if (resolveResult instanceof ImportedResolveResult) {
+          final PyImportedNameDefiner definer = ((ImportedResolveResult)resolveResult).getDefiner();
+          if (definer != null) {
+            myUsedImports.add(definer);
+          }
+        }
+      }
+    }
+
     private void processReference(PyElement node, @Nullable PsiReference reference) {
       if (!isEnabled(node) || reference == null || reference.isSoft()) {
         return;
diff --git a/python/testData/inspections/PyUnresolvedReferencesInspection/functionTypeCommentUsesImportsFromTyping.py b/python/testData/inspections/PyUnresolvedReferencesInspection/functionTypeCommentUsesImportsFromTyping.py
new file mode 100644
index 000000000000..10b8ea2282ad
--- /dev/null
+++ b/python/testData/inspections/PyUnresolvedReferencesInspection/functionTypeCommentUsesImportsFromTyping.py
@@ -0,0 +1,7 @@
+from typing import List, <warning descr="Unused import statement">Optional</warning>
+
+
+def f(x, y):
+    # type: (int, List[int]) -> str
+    y.append(x)
+    return 'foo'
\ No newline at end of file
diff --git a/python/testData/optimizeImports/importsFromTypingUnusedInTypeComments.after.py b/python/testData/optimizeImports/importsFromTypingUnusedInTypeComments.after.py
new file mode 100644
index 000000000000..dd0e3bb71148
--- /dev/null
+++ b/python/testData/optimizeImports/importsFromTypingUnusedInTypeComments.after.py
@@ -0,0 +1,10 @@
+from typing import List, Set
+
+
+def f(x, y):
+    # type: (int, List[int]) -> str
+    y.append(x)
+    return 'foo'
+
+
+xs = {1, 2, 3} # type: Set[int]
diff --git a/python/testData/optimizeImports/importsFromTypingUnusedInTypeComments.py b/python/testData/optimizeImports/importsFromTypingUnusedInTypeComments.py
new file mode 100644
index 000000000000..507921bcc9c4
--- /dev/null
+++ b/python/testData/optimizeImports/importsFromTypingUnusedInTypeComments.py
@@ -0,0 +1,10 @@
+from typing import List, Optional, Set
+
+
+def f(x, y):
+    # type: (int, List[int]) -> str
+    y.append(x)
+    return 'foo'
+
+
+xs = {1, 2, 3} # type: Set[int]
diff --git a/python/testSrc/com/jetbrains/python/PyOptimizeImportsTest.java b/python/testSrc/com/jetbrains/python/PyOptimizeImportsTest.java
index 40fa5081fc2a..9346c602c600 100644
--- a/python/testSrc/com/jetbrains/python/PyOptimizeImportsTest.java
+++ b/python/testSrc/com/jetbrains/python/PyOptimizeImportsTest.java
@@ -81,6 +81,12 @@ public class PyOptimizeImportsTest extends PyTestCase {
     myFixture.checkResultByFile(testName + "/main.after.py");
   }
 
+  // PY-18521
+  public void testImportsFromTypingUnusedInTypeComments() {
+    myFixture.copyDirectoryToProject("../typing", "");
+    doTest();
+  }
+
   private void doTest() {
     myFixture.configureByFile(getTestName(true) + ".py");
     OptimizeImportsAction.actionPerformedImpl(DataManager.getInstance().getDataContext(myFixture.getEditor().getContentComponent()));
diff --git a/python/testSrc/com/jetbrains/python/inspections/PyUnresolvedReferencesInspectionTest.java b/python/testSrc/com/jetbrains/python/inspections/PyUnresolvedReferencesInspectionTest.java
index 72ed58e8d3f6..19b1c24fb1bf 100644
--- a/python/testSrc/com/jetbrains/python/inspections/PyUnresolvedReferencesInspectionTest.java
+++ b/python/testSrc/com/jetbrains/python/inspections/PyUnresolvedReferencesInspectionTest.java
@@ -542,6 +542,12 @@ public class PyUnresolvedReferencesInspectionTest extends PyInspectionTestCase {
     doTest();
   }
 
+  // PY-18521
+  public void testFunctionTypeCommentUsesImportsFromTyping() {
+    myFixture.copyDirectoryToProject("typing", "");
+    doTest();
+  }
+
   @NotNull
   @Override
   protected Class<? extends PyInspection> getInspectionClass() {