Dimethyldichlorosilane has been used to deactivate the hydroxyl groups present in the skeleton of the porous polymer formed from the methacrylic ester of p,p'-dihydroxydiphenylmethane diglycidyl ether and divinylbenzene. The influence of chemical modification of the copolymer on its chromatographic behavior has been studied. The retention indices of five homologous series and test compounds were calculated to determine the selectivity of the packings.