"This was a super cute costume and my daughter got LOTS of compliments wearing it. We just had to do an exchange for a bigger size because the first one we got was way too small. I would say that the 12-24 month costume really fits a 6-12 month baby and the 2T-4T costume really fits a 12-24 month baby. My daughter 18 months old and is not big for her aga and the 2T-4T fit her perfectly. The good thing was that when I had to exchange it they were very accomodating. I did not have to ship the original back and I was not charged anything for the new one so it was pretty hassle free. Luckily I had ordered the original early enough to be able to have another one shipped in time for Halloween."