MissyJG - hi! I'm a fan of C&C's classic tanks, I typically wear them under my Prada cardis! I don't like them too tight and in the past I have always worn a small as I found the XS too, too tight and I'm not big or anything - a US 0 or 2 in clothing! However, I recently ordered directly from their website some classic tanks in small and found that the sizing had really changed. They are way too big and baggy! I would now choose the XS over the S - I would prefer to buy in store but C&C doesn't seem to be stocked anymore in Paris or London!