I came to Amazon to buy the 4T size as we couldn't find them in our local Target where we bought the 2T/3T size.  My 2.5-year-old is not large and the 2T/3T size is so tight on her. She weighs 31 pounds and is in the height range for the 2T/3T size but the smaller size leaves red marks on her legs. The panties held up well for the 2 months we had them - just need a larger size.  I also wish they had more of the characters on them. My daughters favourite pup is Rubble!