Poly(3-dodecylthiophene) films were synthesised electrochemically from a propylene carbonate solution of the monomer, by galvanostatic method and cyclic voltammetry. Electrochemical properties of the resulting polymers were compared with the properties of regioregular head-to-tail (HT) polymer synthesised chemically. The first part of the work is focused on the electrochemical characteristics of HT polymer, namely on dependence of the shape of cyclic voltammograms obtained for redox reaction of the polymer on the film thickness and mean conjugation length. In the second part, the optimum conditions of electrosynthesis have been established. The quartz crystal microbalance measurements carried out during potentiodynamic polymerisation of 3-dodecylthiophene (by cyclic voltammetry) showed that deposition of the polymer film was preceded by dissolution of the gold substrate. At the later stage of the film formation, the oligomers that were initially accumulated in the vicinity of the electrode, attained the crucial lengths and precipitated on the electrode surface. In the case of a slow diffusion of the monomer to the electrode the growing film may be irreversibly overoxidised or/and crosslinked.