Eight different conducting polymer films formed from pyrrole and N-substituted pyrrole derivatives were characterized by cyclic voltammetry, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy. In particular, the XPS of poly[N-butylpyrrole], poly[N-(2-carboxyethyl)pyrrole], poly[N-(6-hydroxyhexyl)pyrrole] and poly[N-(6-tetrahydropyranylhexyl)pyrrole] is reported for the first time. The vapour sorption properties of these films were also examined by forming the films onto the electrodes of thickness-shear mode acoustic wave sensors. The influence of the pendant side chain is apparent in both the electrochemical behaviour, composition, doping level, morphology and the nature and extent of polymer-vapour interactions. The latter can be rationalized by consideration of vapour physical properties and solvatochromic parameters.