The experiment was carried out on 30 Black-and-White Lowland dairy cows divided into 3 groups of 10 to investigate the effect of feeding evening primrose (Oenotheraparadoxa) full fat seeds or oil cake on milk yield and composition. The animals were fed a basic ration consisting of maize silage, sugar beet top silage, meadow hay or green pasture forage (in summer) and concentrate mixture (control group - C) supplemented with evening primrose oil cake (group - O) or full fat seeds (group - S) from the beginning to 100th day of lactation. Average daily milk production was 31.4, 32.1 and 33.2 kg in the C, S and O groups, respectively, but differences between the groups were statistically insignificant. The fat content in milk from cows receiving oil cake (3.88 %) or full fat seeds (3.93 %) with their ration tended to be higher than in the control group (3.78 %) but the level of protein and lactose in milk was similar in all groups.