I was completely finished with diapers before I was two, as was my brother. This was because my mom was used laundered cloth diapers instead of those super-absorbent plastic ones. The problem with modern disposable diapers is that they're so comfortable, the kids never want to stop using them--sometimes they can't even tell if they're wet or not (or so my mom says. I don't have kids so I don't really know). Cloth diapers, on the other hand, are extremely uncomfortable when they're soiled. Thus, potty training probably seems a complete relief to the kids who wear them. Again, so says my mom. And she would know, I guess; she's a mom.