I've used both, and they both have Essential fatty acids.. I was on flaxseed for many months and stopped becuz i suspected it was making my skin overly oily although i was using double the recomened dosage, I did read though, that its almost IMPOSSIBLE for flaxseeed oil to be fresh becuz it turns almost the moment its pressed and then it becomes carcinogenic,,, As for evening primrose this stuff messed up my hormones so bad I had horrid pms and a period that was heavier and more painful than ever so i stopped, but many women have improved PMS and lighter periods from it so you just have to experiment 4 what works with your body... HTH