The authors report experimental data obtained in a study of the sorptive interaction of cyanocobalamin (vitamin B//1//2) with the macroporous molecular sorbent in aqueous and aqueous-organic media. The influence of lower alcohols: methanol (density rho equals 0. 791 g/ml), ethanol ( rho equals 0. 785 g/ml), 1-propanol ( rho equals 0. 804 g/ml), 2-propanol ( rho equals 0. 785 g/ml), and polyethylen glycols (Merck-Schuchardt) of molecular weights from 20,000 to 1,000,000 on sorption of cyanocobalamin was studied. It was shown experimentally that addition of an organic solvent to the cyanocobalamin-macroporous copolymer system lowers the amount of substance sorbed sharply even at a solvent concentration of only 0. 4 M, and the distribution coefficient of cyanocobalamin decreases with increasing complexity of the structure of the organic solvent in the same homologous series. At 0. 4 M alcohol concentration of the distribution coefficient of cyanocobalamin is 175 for methanol, 125 for ethanol, and 25 for 2-propanol.