Re: is flaxseed oil and fish oil basically the same?

They are similar, but not exactly the same in nutritive value.

Flaxseed or linseed oil contains about 50% alpha-linolenic acid ("ALA"), which is an omega-3 fatty acid. It also contains about 30% of linoleic acid ("LA"), which is omega-6, and oleic acid, which is omega-9.

ALA and LA are "essential fatty acids" which are required in the human diet. See:
http://en.wikipedia.org/wiki/Essential_fatty_acid

In the body, ALA and LA are converted to the biologically active forms of longer-chain omega-3 fatty acids eicosapentaenoic acid ("EPA") and docosahexaenoic acid ("DHA"), and the omega-6 fatty acids gamma-linolenic acid ("GLA"), dihomo-gamma-linolenic acid ("DGLA") and arachidonic acid ("AA").

Many food oils contain omega-6 fatty acids, particularly olive and canola oils, so there is rarely a deficiency in the diet.

Fish oil contains typically 30% of EPA and DHA already formed. Unlike with flaxseed oil, these do not have to be built in the body from ALA, so are "ready to use". This is important, because presence in the diet of too much non-omega-3 fatty acids can suppress the formation of EPA and DHA in the body. So you are more certain to get the beneficial EPA and DHA from fish oil than from flaxseed oil. If you do not eat excess fat in your diet, this should not be a problem.

Flaxseed oil also typically contains biologically active green pigments called lignans. These are also beneficial as antioxidants in the diet. See:
http://en.wikipedia.org/wiki/Lignan