A study was carried out on 66 crossbred fatteners (Landrace x (Duroc x Pietrain). Each sex group (boars, gilts and barrows) was represented by 22 animals. The animals were housed in group pens and were fed ad libitum with a mixture containing 13 MJ EM and 17% of crude protein per 1 kg. The study was undertaken to determine the carcass quality after slaughter and the fatty acid composition of loin by sex. In this study, the best carcass composition was observed in boars. There was significant difference (p<0.05) in the meatiness in boar carcasses compared with the meatiness of gilt and barrow groups. Barrow carcasses were characterized by the highest fat and its average of backfat thickness was statistically significantly different (p<0.05) from the backfat thickness of the boar and gilt groups. The analysis of fatty acid composition in m. longissimus dorsi samples shows that in the barrows group, the content of linoleic, linolenic acid and PUFA was significantly lower (p<0.05) in comparison to the content of these fatty acids in the loin of the gilts and boars groups.