I bought this for my 2 1/2 year old daughter.  She's 36 inches tall and weighs 30 pounds.  She usually wears a size 2T.  I bought the size medium and it fit okay, with plenty of room to spare.  It would probably fit a child sized 3T a little better.  I will need to do some minor alterations due to the size at the collar (far too baggy) and poor workmanship in one of the seams.

Overall, it's a very cute costume.  I love the little bow on the skeleton - perfect for my little pirate girl!  However, the boot covers leave a lot to be desired.  They look very odd on her.  We may skip those when she wears the costume.

I don't think it is a very durable costume, but for $15, it's pretty decent.