The objective of this study was to determine the effect of genotype on the selected quality attributes of chicken meat. The proximate chemical composition and technological properties of breast muscles originating from fast growing (Hubbard Flex) and slow growing (Hubbard JA 957) chickens were compared. The muscles for analyses were cut 24 h after slaughter from 6 cocks and 6 hens in each group. Based on the analyses performed, it was confirmed that the breast muscles of the slow growing chickens contained significantly more protein and less fat and cholesterol than the muscles of the fast growing chickens; this is favourable as regards the nutritional aspect. Moreover, they were characterized by a higher water holding capacity and a decreased cooking loss, and this fact is of a significant importance for the manufacturers of the processed poultry meat.