I bought this outfit for my daughter's first birthday. She is a little above average on height (60 %tile) and weight (70 %tile) so I went for the 12-18 months size. All her current clothes that fit well are size 12-18 or 18 months. The top was very long, putting the ruffled part almost at her knees and all but covering up the cute pants which were a little snug but made of stretchy material. Still a very cute outfit though so I'm hoping to invent another reason for her to wear it again when she grows into the top a little more, but we will probably have to rethink the pants.