My 7yo daughter wears a 7/8 slim in pants and is super skinny, but I wanted these to fit for awhile, so instead of the M (7-8yro), I ordered the L (advertised for 9-10yro). Imagine my surprise when they arrived and are SUPER SMALL. Comparing to old clothes, they are equivalent to a 5 or 6, max. So order up 2 sizes, folks. Also note, material is very very thin. Not exactly see through but close, so not for chilly days.