Films of poly(N-vinylcarbazole) (PVCz) were prepared and studied in the presence of different cations using spectroelectrochemical and electrochemical quartz crystal microbalance methods. Evidence for the effect of the cation on both formation and redox behaviour has been obtained. The experimental results have been interpreted by considering the presence of different types of ionic species inside the polymers layer (free anion, screened anion, bound anion and cation).