
My daughter is small for her age due to prematurity. This size 2 was too small for her, while the usual 2T is a little big for her. So I would say the size 2T would be best for an 18 month old. Also, it's a really cute outfit and I'll be saving it for my next baby when he's 18 months old.

Spotted Zebra Girl's Disney Star Wars Marvel Frozen Princess Leggings: Unleash the Fantasy!
46 Review

ZukoCert Fleece Leggings Cashmere 2P B 130 Girls' Clothing for Leggings
61 Review

Kid Nation Unisex Heather Charcoal Girls' Clothing for Leggings
52 Review

Girls' Clothing and Leggings - Govc Winter Fleece Velvet Leggings
49 Review