I wear a size 6 and bought a medium upon reading previous reviews (thanks all) and these were still just a little snug. If you are wearing something tight, there will be panty lines. What I like about these panties at the same time is that they ARE snug and somewhat substantial. I would wear with jeans, but I mostly wear them when I wear running tights. They stay in place and feel like I still have underwear on, but not bothersome. What's the BEST part of these underwear? After I run, I wash them in the sink and they are dry and ready to go the next day.