I usually wear an xxsp in retailer brands. i bought this jacket in a regular size 0 and it fits like a glove. even the sleeves are the right length. it really accents my narrow waist. i imagine it runs very small for those who wear regular sizes. if you are petite this is the jacket for you. the jacket is unlined so i cant wear it in cold weather. it is very nice over a dress with black boots and with skinny jeans. i receive complements every time i wear this item!