I bought this in Medium for my daughter, who takes a women's medium in tops, as do I.  It is so tiny that I checked the tag to see if maybe I had been sent a Girl's size medium by mistake.  I can only conclude that these run really, really small.  That said, it's nicely made and is obviously a quality product.  I won't be returning it because she took off the tag in order to try to try it on (it didn't even fit over her shoulders).