I use Pandora mostly on Wi-Fi, but there are several times a month that I use it on my 4g for several hours at a time. My experience is that it uses a surprisingly small amount of data. I'm on a very small data plan (500 MB) so if it was using a lot I'd know it. But I've never had an issue. I'd say that if you use it for several hours a day, everyday, you'll see some significant data use. But if it's just a moderate amount you'll likely find that it's not bad at all.