The original tread was entered in 2008, looks like it wasn't allowed at the time. But today (March 2013) I managed to do it. Whether an Itunes gift card or App Store card; they both go to the same apple account. I redeemed my gift cards (2 different gift cards from my birthday, 1 Itunes gift card and 1 App Store gift card)) from my Iphone. Then I checked my Imac, I can see the new balance from my Iphone and my Imac at the same time. Same account anyway. I hope this helps.