What is the difference between ipod touch 4g cases and iphone 4g cases?

I'm looking at ipod 4g cases online for christmas, and there's this one case design that i really like, but it is only for iphone 4g. Does it matter if i use it for my ipod touch? Or is the touch thinner than the phone, or something. The design is actually Underworld. (movie.underworld awakening case is fine too) if you could find a store that has an Underworld design for ipod t. 4g, that would be even better!

The touch is thinner and has a different shape than an iPhone (iPhones are more square, iTouch have rounded backs), so it won't fit

Yes, iPod touch 4g is thinner comparable to iPhone and it will not suit if you buy cases not for its own self. It is better to find a good one which is fine for its own.well, you can find it through ebay.

The ipod touch is thinner and the back is more curved, so an iPhone 4 case would not fit.