diff --git a/Classes/AQGridView.m b/Classes/AQGridView.m
index 3f62735..996a2ff 100755
--- a/Classes/AQGridView.m
+++ b/Classes/AQGridView.m
@@ -459,9 +459,16 @@ - (void) updateContentRectWithOldMaxLocation: (CGPoint) oldMaxLocation gridSize:
 
 - (void) handleGridViewBoundsChanged: (CGRect) oldBounds toNewBounds: (CGRect) bounds
 {
+    CGPoint oldOffset = self.contentOffset;
 	CGSize oldGridSize = [_gridData sizeForEntireGrid];
 	BOOL wasAtBottom = ((oldGridSize.height != 0.0) && (CGRectGetMaxY(oldBounds) == oldGridSize.height));
 
+    // cell height may change on rotation
+    if ( _flags.dataSourceGridCellSize == 1 )
+	{
+        [_gridData setDesiredCellSize: [_dataSource portraitGridCellSizeForGridView: self]];
+	}
+
 	[_gridData gridViewDidChangeBoundsSize: bounds.size];
     _flags.numColumns = [_gridData numberOfItemsPerRow];
 	CGSize newGridSize = [_gridData sizeForEntireGrid];
@@ -478,6 +485,19 @@ - (void) handleGridViewBoundsChanged: (CGRect) oldBounds toNewBounds: (CGRect) b
 			self.contentOffset = contentRect.origin;
 		}
 	}
+    else if (!wasAtBottom && !CGPointEqualToPoint(oldBounds.origin, CGPointZero) && !CGSizeEqualToSize(oldGridSize, CGSizeZero))
+    {
+        // If not at the bottom or top (they are handled above and in updateContentRectWithOldMaxLocation)
+        // and we have data to work with (sometimes we can start with the oldSize == 0),
+        // constentOffset.y needs to be reset to be proportional to the new height. Then snap it to the nearest cell boundry.
+        
+        CGFloat proportionalY = newGridSize.height * (oldOffset.y / oldGridSize.height);
+        CGRect cellRect = [_gridData cellRectForPoint:CGPointMake(self.contentOffset.x, proportionalY)];
+        CGFloat newY = (proportionalY < (cellRect.origin.y + (cellRect.size.height / 2.0f))) ?
+        cellRect.origin.y : cellRect.origin.y + cellRect.size.height;
+        self.contentOffset = CGPointMake(self.contentOffset.x, newY);
+    }
+
 
 	[self updateVisibleGridCellsNow];
 	_flags.allCellsNeedLayout = 1;
@@ -545,7 +565,7 @@ - (void) setFrame: (CGRect) newFrame
 	[super setFrame: newFrame];
 	CGRect newBounds = self.bounds;
 
-	if ( newBounds.size.width != oldBounds.size.width )
+    if ( !CGSizeEqualToSize(newBounds.size, oldBounds.size) )
 		[self handleGridViewBoundsChanged: oldBounds toNewBounds: newBounds];
 }