The aim of the present study was to determine the profile of fatty acids in muscle lipids of freshwater fish: carp (Cyprinus carpio L.), rainbow trout (Oncorhynchus mykiss Walb.), bream (Abramis brama L.) and tench (Tinca tinca L.) from markets of Olsztyn (north-eastern Poland). Separation and identification of fatty acids were made using gas chromatography. The content of some fatty acids varied among species. Generally, palmitic acid (15.6%-19.5%) was the most abundant saturated fatty acid (SFA). The main monounsaturated fatty acid (MUFA) was oleic acid (20.7%-42.7%). Linoleic (4.6%-8.0%), arachidonic (AA) (0.8%-6.6%), docosahexaenoic (DHA) (1.7%-15.9%) and eicosapentaenoic (EPA) (1.2%-8.8%) acids were the predominant polyunsaturated fatty acids (PUFA). There were no significant differences (p>0.05) in the content of SFA (24.3%-28.7%) among the fish species. The content of MUFA in muscle lipids of carp (55.0%) was significantly higher (p≤0.01) than in the lipids of the other fish examined (35.8%-38.3%). Bream and rainbow trout (26.6% and 27.7%, respectively) contained significant more n-3 PUFA than carp (4.7%) and tench (20.5%) (p≤0.01). Total n-6 PUFA ranged between 8.4% (rainbow trout) and 12.9% (tench). Significant differences in n-6 PUFA content were only observed in the case of these fish (p≤0.01). The differences in the n-3/n-6 ratio (rainbow trout (3.3) > bream (2.6) > tench (1.6) > carp (0.4)) were statistically significant (p≤0.01).