The aim of the study was to determine the effect of the inclusion of 2%, 4% and 6% extruded flaxseed in the diet of fattening pigs on theirgrowth performance parameters, carcass parameters, and selected blood parameters. The experiment was conducted on 160 weaners(from about 30 kg to about 110 kg BW) assigned to four experimental groups of 40 animals each (5 replicates with 8 individuals each).The animals in control group received a diet in which the source of fat was soybean oil. The other groups received extruded flaxseed (FE)in place of soybean meal in the amount of 2% (group 2FE); 4% (group 4FE) and 6% (group 6FE). soybean oil was added to the dietsin the experimental treatments to obtain equal amounts of fat. The inclusion of 2% and 4% extruded flaxseed in the diet of fatteners inplace of soybean meal significantly improved the digestibility of basic nutrients, i.e. ether extract (by about 5%) and dietary fibre (bymore than 20%) and led to better growth performance (higher BW by about 11%; higher ADG by about 20% and lower FCR by about12%) vs group C. In the groups with 2% and 4% extruded flaxseed there was also an increase in the lean meat content of the carcasses(by about 6%) and the thickness of the backfat (by about 6.5%) vs group C. The inclusion of extruded flaxseed did not affect the animals’condition, as indicated by the haematological and biochemical parameters of the blood, which were within reference ranges. The resultsfor production, nutrient digestibility and carcass analysis between groups 2FE and 4FE were similar, and at this stage of research indicatethat the use of 2% extruded flaxseed is economically more justified.