Abstract. A total of 60 drakes out of three flocks of conservative Miniduck (K2), Polish Pekin (P33), native Pekin population type A3 and two breeding strains (A55, P66), aged seven weeks, were used for comparison. The content of protein, lipids, moisture, essential amino acids, fatty acids and cholesterol were estimated. There were differences among flocks in all biochemical parameters. The muscles of A55 and P66 comprised more protein and less moisture than P33 and A3 muscles. The P33 breast muscles comprised the least of lipids (0.8% v/s 1.16–1.32%), however A55 of cholesterol (71.21mg/100g v/s 82.23–111.82 mg/100g). The isoleucine (ILE) and valine (VAL) were amino acids which limited the biological value of meat proteins from breast muscles of A3, P33 and K2, however tryptophan (TRP) for A55, P66 muscles. The unsaturated fatty acids (UFA) were predominant for all flocks (50.12–60.64%), the P66 muscles contained the most of UFA and P33 the most of saturated fatty acids (SFA). The highest level of polyunsaturated fatty acids (PUFA) was established in K2 muscles. The PUFA/SFA and n-6/n-3 PUFA ratios were 0.63–0.84 and 3.22–5.85 respectively. The lipids of A55 were characterized by the best fatty acid profile among the investigated muscles. Taking into consideration the nutritive value of proteins, cholesterol content and profile of fatty acids, A55 breast muscles appeared to be the most favourable from the human health point of view.