We ordered a L for my 8 yo whose measurements mostly fall into medium but girth (shoulder to crotch) measurement is in the large size category. It fits well - there is room for her to grow into it and the sleeves are a tad long which is fine but it doesn't look too large for her. She loves that it's comfortable and cozy. Good purchase for us!
I bought this for my 3 year old. She's always cold in class, but I wasn't willing to spend the $30 the local store was charging for a toddler's warm up sweater. Some of the reveiws of the eurotard brand child's sweater offered on this site said it was itchy so I went with this one even though I prefered the look of the other, as my daughter has sensitive skin. This sweater does not seem itchy at all and it looks really cute on her. I ordered the toddler size and it fits her very well with just a little growing room in the arms. In street clthes she wears a 3T shirt, so the sizing seems spot on. I'm pleased with this purchase.