Blends containing poly(N-vinyl-2-pyrrolidone) (PVP) and poly(hydroxyethyl methacrylate) (PHEMA) with (styrene-co-dimethyl itaconate) (Sty-co-DMI) and(styrene-co-diethylitaconate) (Sty-co-DEI) copolymers of three different compositions were studied. One Tg value over the whole range of compositions is observed for the majority of the blends, what is indicative of compatibility. The Gordon-Taylor k(GT) and the Couchman k(C) parameters were determined for all the blends in order to compare the strength of the interactions. The effect of the side chain structure of the copolymer on the miscibility of these blends is analyzed.