The experiment was performed according to a 2 x 2 factorial design with breed and level of nutrition as factors affecting fat metabolism in pigs. Two groups of gilts, each comprising 4 Polish Large White (PLW) and 4 Synthetic Line 990 (L990) animals, were fed from 60 to 105 kg body weight on the experimental diet at 85% or 95% of assumed ad libitum intake. The diet contained 2% of linseed, 0.5% rapeseed and 0.5% fish oils as the source of n-3 fatty acids (FA). The carcass protein content was smaller and backfat thickness greater in L990 than in PLW pigs. Also the intramuscular fat content in the biceps femoris (BF) and longissimus dorsi (LD) muscles and their contents of total FA, saturated fatty acids, monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) were higher or tended to be higher in L990 than in PLW pigs, the differences between the breeds being more pronounced in the BF muscle. The n-6/n-3 PUFA ratio tended to be lower in the LD muscle, whereas in the BF muscle, it was lower in L990 than in PLW pigs. Feeding at the 85% level resulted in smaller backfat thickness and carcass fat content in animals of both breeds. Gene expression of stearoyl-CoA desaturase in both muscles was higher in L990 pigs, which could have resulted in the higher MUFA and PUFA contents in this breed. Gene expression of fatty acid-binding protein 4 and peroxisome proliferator-activated receptor were affected both by breed and feeding level only in the BF muscle.