This study investigated effects of linseed or fish oilenriched finishing diets on the polyunsaturated fatty acids (PUFA) composition in dorsal muscle tissues of pond-cultured common carp (Cyprinus carpio). After 180 days of dietary exposure to cereal diet containing vegetable oil (1%), carp were exposed to 7% linseed (LO) or 7% fish oil-enriched (FO) finishing diets for 30 days. FO supplied 17 and 20 mg fish À1 day À1, respectively, of the long-chain n-3 fatty acids eicosapentaenoic and docosahexaenoic acid for 30 days and doubled long-chain PUFA concentrations in carp of the FO pond. The increased supply of short-chain PUFA in LO resulted in higher short chain, but not long-chain PUFA, showing that there was very little PUFA conversion. Thus, dietary short-chain PUFA could not compensate for the low levels of dietary long-chain PUFA in LO. However, moderate supply of dietary long-chain PUFA in finishing diets for 30 days is very efficient in increasing nutritionally important long-chain PUFA concentrations in carp.