Are omega 3s from flaxseed useful to the body?

I get roughly 20-30 grams of omega 3 fatty acids per week. Less than 5 of these grams come from fish. Most come from ground flaxseeds and olive oil. I read that only omega 3s in the form of DHA and EPA produce the desirable effects. Is this true? Are the omega 3s from ground flaxseeds healthy in another way?