--- a/toolkit/content/widgets/scrollbox.xml
+++ b/toolkit/content/widgets/scrollbox.xml
@@ -553,31 +553,40 @@
     </implementation>
 
     <handlers>
       <handler event="wheel"><![CDATA[
         if (this.orient == "vertical") {
           if (event.deltaMode == event.DOM_DELTA_PIXEL)
             this.scrollByPixels(event.deltaY);
           else if (event.deltaMode == event.DOM_DELTA_PAGE)
-            this.scrollByPage(event.deltaY);
+            this.scrollByPage(event.lineOrPageDeltaY);
           else
-            this.scrollByIndex(event.deltaY);
+            this.scrollByIndex(event.lineOrPageDeltaY);
         }
         // We allow vertical scrolling to scroll a horizontal scrollbox
         // because many users have a vertical scroll wheel but no
         // horizontal support.
         // Because of this, we need to avoid scrolling chaos on trackpads
         // and mouse wheels that support simultaneous scrolling in both axes.
         // We do this by scrolling only when the last two scroll events were
         // on the same axis as the current scroll event.
         // For diagonal scroll events we only respect the dominant axis.
         else {
           let isVertical = Math.abs(event.deltaY) > Math.abs(event.deltaX);
-          let delta = isVertical ? event.deltaY : event.deltaX;
+          let delta;
+          if (event.deltaMode == event.DOM_DELTA_PIXEL) {
+            delta = isVertical ? event.deltaY : event.deltaX;
+          } else {
+            // Use low resolution delta value for line or page scroll because
+            // neither scrollByIndex() nor scrollByPage() treats delta value as
+            // double.  It treats delta just as 1, -1 or 0.
+            delta = isVertical ? event.lineOrPageDeltaY :
+                                 event.lineOrPageDeltaX;
+          }
           let scrollByDelta = isVertical && this._isRTLScrollbox ? -delta : delta;
 
           if (this._prevMouseScrolls.every(prev => prev == isVertical)) {
             if (event.deltaMode == event.DOM_DELTA_PIXEL)
               this.scrollByPixels(scrollByDelta);
             else if (event.deltaMode == event.DOM_DELTA_PAGE)
               this.scrollByPage(scrollByDelta);
             else