The objective of the study was to determine the inter-specific differences in the contents of Mn, Cu, Zn, Fe, Ca, Mg, Na, and K, as well as in fatty acids in muscles of rainbow trout (Oncorhynchus mykiss Walb.), carp (Cyprinus carpio L.), and salmon (Salmo salar L.) purchased at a market in the city of Olsztyn (Poland). Na and K were determined using an emission flame photometry. The other elements were analyzed using an AAS method. Fatty acids were determined using gas chromatography. The carp fish was characterized by the highest content of Mn, Fe, and Ca (p ≤ 0.01). Also, it was found that the carp was a rich source of Zn, and the significant differences were found only if compared to the salmon (p ≤ 0.01). As for the other elements determined, no significant interspecific differences (p > 0.05) were found. In the lipids contained in the muscles of rainbow trout examined, the highest content of saturated fatty acids (26.79 %) (p ≤ 0.05) was determined. The highest amount of monoenoic acids was reported in the lipids in the muscle tissue of carp (51.45 %) (p ≤ 0.01). Among the saturated fatty acids, the palmitic acid was a predominant fatty acid (C16:0) whereas the monoenoic fatty acids were represented by the oleic acid (C18:1). The differences in the content of n-6 polienoic fatty acids were found only between the carp and the salmon (p ≤ 0.05). The linoleic acid (C18:2) prevailed among the n-6 polienoic fatty acids. The salmon and rainbow trout (p ≤ 0.01) were a rich source of n-3 polienoic fatty acids (19.99 % and 23.18 %) and EPA (6.04 % and 5.17 %) (p ≤ 0.01) whereas the trout had significantly more DHA (14.50 %) (p ≤ 0.01).