The objective of the investigations was to access the effect of modified starch added to the diet of rats on some selected nutritional parameters, as well as on the bioavailability of antioxidant vitamins A and E. The biological experiments were performed using 24 male rats of a Wistar race. The rats were divided into two groups, and fed using semi-purified diets containing starch addition, during a period of 50 days. The diets applied to experimental animals differed in the type of potato starch (non-modified or chemically modified, i.e. an acetylated distarch adipate), but the levels of vitamins A and E in the diets were identical as recommended. It was stated that the addition of high amounts of modified starch to the diet of rats caused a decrease in the food conversion efficiency, and it also limited rates of body mass gain in rats; though, it did not produce any effect of reducing the bioavailability of vitamins A and E.