Abstract: Modified polyurethanes containing perfluoroaliphalic groups which are obtained by reacting oligo(poly)urethanes containing free hydroxyl or isocyanate groups and perfluoroaliphatic groups with di/polyfunctional polysiloxanes at elevated temperatures with conversion of all the reactive groups of the urethane are used for the oil- and water-repellent finishing of fiber materials, conferring on these materials thus treated not only laundering- and drycleaning-stable effects but also in particular a very soft, full hand of very good surface smoothness, these excellent hand effects being further optimized by the addition of a polyethylene dispersion and/or of further customary textile assistants, in particular water-repellent fluorocarbon compounds.