I needed this costume within a short amount of time, so I had to order a medium because there was no prime 2 day shipping available for the size small. If you have a small waist, but bigger bust i would suggest going with the size that matches your waist if you want to show your curves more because the corset wasn't able to be adjusted a lot. Something to note is that the buttons in the front are very hard to hook. For reference my hips are about 36 inches and the shorts that came with the medium fit good, but shows a lot. Overall its a very cute costume.