The experiment was conducted on 640 Cobb chickens allocated to 16 groups, 5 replications of 4 males and 4 females each. Chickens from 22 to 42 days of age were fed diets containing 50, 47, 45 and 42 g·kg^-1 of rapeseed oil and 0, 3, 5 and 8 g·kg^-1 fish oil, respectively. The diets were supplemented with 0, 40, 150 and 300 mg · kg^-1 of α-tocopheryl acetate. At the end of the experiment, the chickens were killed and samples of breast meat were prepared, frozen (-20^oC) and stored for 6 months. Samples were analysed for fatty acid composition, thiobarbituric acid reactive substances (TBA-RS), and α-tocopherol content. Fish oil positively affected the performance of chickens, elevated the content of stearic (C_18:0) and eicosapentaenoic (C _20:5,n-3) acids, and lowered the polyunsaturated fatty acid (PUFA) n-6:n-3 ratio in stored breast meat. Fish oil at 8 g·kg^-1 in the diet decreased linolenic acid (C_{18:3, n-3}), unsaturated fatty acid, and n-6 PUFA contents, increased saturated fatty acid (SFA) content in lipids and lowered the PUFA:SFA ratio. The addition of 150 or 300 mg· kg^-1 α-tocopheryl acetate to the diets increased the level of vitamin E in stored breast meat and lowered the TBA-RS value. The levels of fish oil and vitamin E used had no effect on the sensory properties of meat.