RUNS SMALL! Size says 2T. My daughter did wear this when she was a 2T, but it was snug and the length is short too. It could probably even work for 12-18 months, but that depends on the size of your 12-18 months in length. It’s so adorable. The back crisscross is a snap closure and easily slips over their head. It’s very soft and the gray is just so sweet! Pair it with a jean jacket and some brown boots and she will be good to go for fall as well as a summer look.