Kids are being warned to be extra careful when downloading stuff from the internet to their mobile phones.
Experts have been checking the websites aimed at children and found that lots of them don't have enough information about how much they cost.
The experts were able to close eight websites in the UK, force 27 to change what was on the sites and are keeping an eye on another 40.
Lots of them had stuff on them that was too old for kids but had no age limits.
Dodgy sites often offered money for working from home, or "free" prize draws that weren't as free as they seemed.
Some sites were also bad because they didn't make it clear how to cancel something you decided didn't actually want.