The aim of the study was to determine the impact of caponisation of Polbar (Pb) and Greenleg Partridge (Zk) breeds on the production performance, carcass composition, and the nutrient content and fatty acid profile in the breast and thigh muscles and abdominal fat. From 18 weeks of age to the end of the experiment, the Zk capons were significantly heavier than the cocks. The Zk capons had higher (p≤0.05) weight and share of breast and leg muscles. At 24 weeks of age, we noted an increase in the total content of n-3 PUFA and linolenic acid C18:3 in the breast muscles of the Zk and Pb capons. The content of PUFA and n-3 PUFA in thigh muscles and the n6/n3 ratio were reduced in the Pb capons at 24 weeks of age, compared with the Zk cocks. Caponisation of the Pb cocks had a beneficial effect on the final body weight, feed intake, and slaughter characteristics, in comparison with the non-caponised birds of this breed. A tendency towards an increased total share of PUFA and MUFA, a significantly higher content of n-3 PUFA, and a lower (p≤0.05) n-6/n-3 ratio were found for the breast muscles of the Pb capons. Both breeds are a good material for production of capons. The meat of the capons of both breeds exhibited a beneficial, higher PUFA/SFA ratio, higher n-3 PUFA and MUFA content, and a more favourable n-6/n-3 ratio.