We were so excited to receive this costume.  However, we ordered the Child's medium.  My son is about 60 lb and 51 inches tall - smaller than your average 8 year old, I would say - he wears size 7 clothing.  He doesn't have a big head either.  The mask completely smashed his nose.  So I cut the clear plastic out and the mask is so flat that without the plastic, his nose was fine and able to protrude normally, but now his lips also stuck through!  What a e of money!  Don't dissapoint your son and buy this costume.