Viscoelastic properties of intrinsically conducting polymers depend on different factors, among them polymer structure, ionic and solvent population and film thickness. During a voltammetric cycle, electrochemical reactions involve changes of these factors. Consequently, the viscoelastic properties are expected to be changed. Electrochemical quartz crystal microbalance with motional resistance monitoring were employed to calculate the instantaneous resonant frequency/motional resistance ratio (df(r/)dR(m)) during the electrochemical processes of acoustically thin films of poly(o-toluidine). df(r)/dR(m) is defined as the energy dissipation factor and shows values around similar to 10 Hz Omega(-1) for a net liquid-loading effect on resonator electrode. Therefore, as this value is larger the film deposited on resonator electrode is expected to be more rigid. The experimental results showed in this work points to this assumption. Viscoelastic state of acoustically thin films of poly(o-toluidine) were investigated through redox reactions, in different electrolytes and scan rates potential perturbations. Finally, viscoelastic changes of a relaxed POT and packed POT was compared. The viscoelastic aspects of poly(o-toluidine) here investigated can help to understand and adjust the signal transduction of (bio) sensors or for composite supercapacitors where the mechanical properties of the different organic layers can limit the performances of the electrochemical system. (C) 2015 Elsevier Ltd. All rights reserved.