The objective of the research study was to characterize the quality of carcasses and meat of Wrzosówka lambs fed a linseed-supplemented diet. The research study comprised 20 lambs (rams) from a stock covered by a genetic resources conservation programme. At the age of 120 days, the animals were divided into two feeding groups, 10 rams in each group. They were fed hay and straw ad libitum and about 0.3 kg of mixed concentrate per one lamb. In the control group, the mixed concentrate was a C-J mix, whereas in the experimental group, this was the CJ mix with 5 % of flax seed fodder added. As soon as the fattening period ended, the animals were slaughtered. The evaluation of the slaughter performance included: carcasses assessment of slaughtered animals, determination of the content of carcass cuts, and determination of the tissue composition of leg. The chemical composition was performed using the longest dorsal muscle. It was found that the feed applied had no effect on the gains in body weight of the lambs and on their carcass parameters. Based on the analysis of the tissue composition of leg, it was found that, in the case of the animals fed the concentrate with 5 % of linseed added, the fat content in this cut was ca. 1.5 times higher. No differences were reported in the major composition of meat. However, the feed type had an effect on the fatty acid profile. The intramuscular fat of lambs fed the linseed-enriched feed mix contained more linolenic acid (about 0.68 p.p.), which contributed to the increase in the total content of n-3 PUFA by ca. 1.2 p.p., thus reducing the n-6/n-3 ratio, compared to the control group, by 3.11 and 4.99, respectively.