Electrode deposits of a polythiophene with particularly interesting characteristics, i.e., poly[4,40-bis(butylsulphanyl)-2,20-bithiophene],have been generated in the presence of different supporting electrolytes. The formation of the coatings has been studied bycoupling conventional electrochemical techniques with quartz crystal microbalance measurements. The results of simultaneousvoltammetric or chronoamperometric and microgravimetric experiments allow us to show the influence exerted by the nature of thesupporting electrolyte on the polymerisation and concomitant charging–discharging processes of the conducting polymer.