A study of the electrochemical preparation of conductive composite films from polypyrrole and non-conducting polyurethane resin is presented. Pyrrole and dopants can penetrate through a polyurethane substrate (pre-coated on a Pt electrode by casting) and electropolymerize on the Pt surface due to the swelling of the coating by the electrolyte solution (dry acetonitrile mixed with ethylene glycol). Cyclic voltammograms show that the diffusion process in polyurethane is inhibited for larger anions.