Atactic and isotactic polypropylene (APP and IPP), and ethylene-propylene copolymers (EP), functionalized by reacting the molten polymer with diethylmaleate (DEM) in the presence of dicumylperoxide (DCP), have been blended with poly(vinylchloride) (PVC) and polystyrene (PS). These mixtures have been investigated by means of infrared spectroscopy at different compositions in the region of carbonyl absorption. The features of this last band in the mixture suggest the occurrence of intermolecular interactions involving mainly the carbonyl groups of the functionalized polymer and the methine hydrogens of PVC.