Three groups of 12 broiler chickens were fed from 8 to 21 day of life wheat-based, xylanase-supplemented diets containing 80 g crude fat/kg; control diet contained lard, diet L 80 g linseed, diet R 100 g rapeseed per kg. Growth performance data were recorded, than 6 chickens from each group were killed after 17 h of food deprivation, and 3 parts of small intestine were incised, fixed and mounted in paraplast. The histomorphometry of villi, crypts and tunica muscularis and submucosa was performed using light microscopy. Birds from group L were significantly heavier than from R group (P<0.05), due to higher feed intake, other differences were not significant. Histological observations on small intestinal mucosa showed elongation of the villi, greater depth of crypts and greater thickness of intestinal wall in jejunum and ileum in L and R chickens in comparison with control group (P<0.05). The changes in morphological structure of intestinal wall may indicate on a shift in a site of the absorption of nutrients within the digestive tract of chickens fed diets with linseed and rapeseed.