diff --git a/content/canvas/src/CanvasRenderingContext2D.cpp b/content/canvas/src/CanvasRenderingContext2D.cpp
index 36c98cf66fc8..9aeb494a477a 100755
--- a/content/canvas/src/CanvasRenderingContext2D.cpp
+++ b/content/canvas/src/CanvasRenderingContext2D.cpp
@@ -2355,12 +2355,36 @@ CanvasRenderingContext2D::MeasureText(const nsAString& rawText,
   return new TextMetrics(width);
 }
 
-void CanvasRenderingContext2D::AddHitRegion(const HitRegionOptions& )
-{}
+void
+CanvasRenderingContext2D::AddHitRegion(const HitRegionOptions& options, ErrorResult& error)
+{
+  // remove old hit region first
+  RemoveHitRegion(options.mId);
 
-void CanvasRenderingContext2D::RemoveHitRegion(const nsAString&)
-{}
+  // for now, we require a fallback element
+  if (options.mControl == NULL) {
+    error.Throw(NS_ERROR_DOM_NOT_SUPPORTED_ERR);
+    return;
+  }
 
+  // check if the control is a descendant of our canvas
+  HTMLCanvasElement* canvas = GetCanvas();
+  if (!canvas || !nsContentUtils::ContentIsDescendantOf(options.mControl, canvas)) {
+    error.Throw(NS_ERROR_DOM_NOT_SUPPORTED_ERR);
+    return;
+  }
+
+  // finally, add the region to the list if it has an ID
+  if (options.mId.Length() != 0) {
+    mHitRegionsOptions.PutEntry(options.mId)->mElement = options.mControl;
+  }
+}
+
+void
+CanvasRenderingContext2D::RemoveHitRegion(const nsAString& id)
+{
+  mHitRegionsOptions.RemoveEntry(id);
+}
 
 /**
  * Used for nsBidiPresUtils::ProcessText
diff --git a/content/canvas/src/CanvasRenderingContext2D.h b/content/canvas/src/CanvasRenderingContext2D.h
index 263058bba7be..314ab5e2be13 100644
--- a/content/canvas/src/CanvasRenderingContext2D.h
+++ b/content/canvas/src/CanvasRenderingContext2D.h
@@ -186,7 +186,7 @@ public:
   TextMetrics*
     MeasureText(const nsAString& rawText, mozilla::ErrorResult& error);
 
-  void AddHitRegion(const HitRegionOptions& options);
+  void AddHitRegion(const HitRegionOptions& options, mozilla::ErrorResult& error);
   void RemoveHitRegion(const nsAString& id);
 
   void DrawImage(const HTMLImageOrCanvasOrVideoElement& image,
@@ -684,6 +684,26 @@ protected:
   uint32_t mInvalidateCount;
   static const uint32_t kCanvasMaxInvalidateCount = 100;
 
+  /**
+    * State information for hit regions
+    */
+
+  struct RegionInfo : public nsStringHashKey
+  {
+    RegionInfo(const nsAString& aKey) :
+      nsStringHashKey(&aKey)
+    {
+    }
+    RegionInfo(const nsAString *aKey) :
+      nsStringHashKey(aKey)
+    {
+    }
+
+    nsRefPtr<Element> mElement;
+  };
+
+  nsTHashtable<RegionInfo> mHitRegionsOptions;
+
   /**
     * Returns true if a shadow should be drawn along with a
     * drawing operation.
diff --git a/dom/webidl/CanvasRenderingContext2D.webidl b/dom/webidl/CanvasRenderingContext2D.webidl
index 565f34477a73..18598cee1828 100644
--- a/dom/webidl/CanvasRenderingContext2D.webidl
+++ b/dom/webidl/CanvasRenderingContext2D.webidl
@@ -116,7 +116,7 @@ interface CanvasRenderingContext2D {
   void drawImage((HTMLImageElement or HTMLCanvasElement or HTMLVideoElement) image, double sx, double sy, double sw, double sh, double dx, double dy, double dw, double dh);
 
   // hit regions
-  [Pref="canvas.hitregions.enabled"] void addHitRegion(optional HitRegionOptions options);
+  [Pref="canvas.hitregions.enabled", Throws] void addHitRegion(optional HitRegionOptions options);
   [Pref="canvas.hitregions.enabled"] void removeHitRegion(DOMString id);
 
   // pixel manipulation