Thin films of CNT/PANI composites have been deposited potentiostatically by electrochemical polymerization from a solution of CNT dispersed in aniline monomer and H2SO4 on ITO coated glass substrates. H2SO4 concentration in aniline monomer solution has been varied and its effect on electrochemical properties of films has been studied. To elucidate information about the degree of surface disorder, surface growth mechanism and the kinetics of electrochemical reactions at the surfaces, fractal dimensions has been evaluated using two electrochemical techniques: cyclic voltammetry and electrochemical impedance spectroscopy. It is observed that as acid concentration in the deposition solution increases, fractal dimension of the deposited film varies from D-F = 1 corresponding to a series of isolated islands, increasing to 2 for a planar 2D configuration for smooth surfaces and finally reaching a value of 2< D-F <3 for rough and porous surface of the electrodes. Results obtained from both the techniques are found to be in good agreement with the fractal dimension values lying between those for smooth and porous/rough surface. (C) 2017 Elsevier Ltd. All rights reserved.