An electrochemical quartz crystal microbalance (EQCM) was used to investigate the formation of polymeric products resulting from electrooxidation in aqueous solutions of phenolic compounds on the surface of Au and Pt electrodes. The studied compounds were phenol; m-cresol; 2,5-dimethylphenol and 2,3,5-trimethylphenol. The polymerization process was studied as a function of the methyl substitution in the phenolic structure. Electrochemical quartz crystal microbalance studies show that the polymer formed from substituted phenols is more passivating than that from the non-substituted phenol. In any case, the largest amount of mass was deposited during the first voltammetric cycle and the Pt electrode was more active than the Au electrode for the organic electrooxidation process. FT-IR spectroscopy showed that the films formed upon phenol and m-cresol electrolysis were also oxidized.