Plasma processes have revealed to be, in the last decades, among the more powerful tools utilized for surface modification of polymers intended to be used in the biomedical field. In particular, two main plasma processes have been widely used: the deposition of thin films and the grafting of functional groups (plasma treatments). For this work two different polymers, polyethylene terephthalate and polystyrene were grafted with nitrogen-containing groups to enhance cell response. NH(2) functionalities were used as anchor groups for the immobilization of galactosamine. Hepatocytes cells, HepG2, were seeded onto modified samples to assess cell biocompatibility of N- and Gal-containing substrates. For both polymers, cell culture results clearly show that cells grown on N-grafted and Gal-immobilized substrates displayed a different cell behaviour.