Poly[3-(omega-4-pyridylalkyl)thiophenes] (P(P(n)T); n = 2, 5, 7, 9, 11) were prepared on the surfaces of Pt disk electrodes by oxidative electropolymerization of the respective monomers. Scanning electron microscopy and cyclic voltammetry were used to investigate the surface structure and electrochemical properties of the polymer-modified electrodes. Apparent diffusion coefficients D-app for charge transfer in the polymer matrices were measured by chronoamperometry, and revealed a dependency on both the porous structure of the polymers (which is determined by the length of the alkyl chains between thiophene and pyridyl groups), and the nature of the supporting electrolytes. A.c. impedance spectra depended on the doped state of the films and the nature of the supporting electrolytes. In oxidized polymers, the charge transfer processes within the bulk polymers and at interfaces are controlled by both kinetic factors and diffusion, while for the reduced films kinetic factors predominate.