diff --git a/jquery.appear.js b/jquery.appear.js
index ff0b764..a7ca39c 100644
--- a/jquery.appear.js
+++ b/jquery.appear.js
@@ -15,9 +15,11 @@
   var check_lock = false;
   var defaults = {
     interval: 250,
-    force_process: false
+    force_process: false,
+    viewport: window
   }
   var $window = $(window);
+  var $viewport = $(defaults.viewport);
 
   var $prior_appeared;
 
@@ -45,16 +47,26 @@
       return false;
     }
 
-    var window_left = $window.scrollLeft();
-    var window_top = $window.scrollTop();
+    var is_win = $viewport[0] === window;
+
+    var scroll_top = $viewport.scrollTop();
+    var scroll_left = $viewport.scrollLeft();
+
+    var viewport_offset = $viewport.offset();
+    var viewport_offset_top = is_win ? 0 : viewport_offset.top;
+    var viewport_offset_left = is_win ? 0 : viewport_offset.left;
+
     var offset = $element.offset();
-    var left = offset.left;
-    var top = offset.top;
+    var top = is_win ? offset.top : Math.abs(viewport_offset_top - offset.top - scroll_top);
+    var left = is_win ? offset.left : Math.abs(viewport_offset_left - offset.left - scroll_left);
+
+    var extra_offset_top = $element.data('appear-top-offset') || 0;
+    var extra_offset_left = $element.data('appear-top-offset') || 0;
 
-    if (top + $element.height() >= window_top &&
-        top - ($element.data('appear-top-offset') || 0) <= window_top + $window.height() &&
-        left + $element.width() >= window_left &&
-        left - ($element.data('appear-left-offset') || 0) <= window_left + $window.width()) {
+    if (top + $element.height() >= scroll_top &&
+        top - extra_offset_top <= scroll_top + $viewport.height() &&
+        left + $element.width()  >= scroll_left &&
+        left - extra_offset_left <= scroll_left + $viewport.width()) {
       return true;
     } else {
       return false;
@@ -76,7 +88,9 @@
           setTimeout(process, opts.interval);
         };
 
-        $(window).scroll(on_check).resize(on_check);
+        $viewport = $(opts.viewport);
+        $viewport.scroll(on_check);
+        $window.resize(on_check);
         check_binded = true;
       }