The aim of the study was to determine the degree of sorption of organic (Se-met) and inorganic (Se-inorg) forms of selenium on wheat, rye and oats bran in variable environmental conditions (pH 1.8, pH 6.6, pH 8.7). The content of dietary fibre (NDF) of cereals bran and its fraction was determined in order to explain the process of selenium sorption in connection with chemical structure and fractional composition. It was shown that the value of selenium sorption ranged from 21 to 36% for wheat and rye bran, while that for oats bran was from 7 to 19%. The studied preparations have a higher sorption capacity in the environment corresponding to oral cavity (pH 6.6) and a lower one in the environment corresponding to stomach juice (pH 1.8). It was found that inorganic selenium was more intensively bound by the tested preparations than the organic form. Sorption of selenium by cereals bran depended not only on the total content of dietary fiber but also on its fractional composition.