Hydrophobically modified polymer compositions contain at least one polymer based on one or more ethylenically unsaturated monomers, in the form of an aqueous polymer dispersions or water-redispersible polymer powder prepared therefrom, further containing, a) one or more silanes, polysilanes, oligosiloxanes, polysiloxanes, carbosilanes, polycarbosilanes, carbosiloxanes, polycarbosiloxanes, polysilylenedisiloxanes, and b) one or more fatty compounds from the group of the fatty acids having from 8 to 22 carbon atoms, their metal soaps, their amides, and their esters with monohydric alcohols having from 1 to 8 carbon atoms, with glycol, with polyglycol, with polyalkylene glycol, with glycerol, with mono-, di-, or triethanolamine, or with monosaccharides.