Polyaniline (PANI), poly(3,4-ethylenedioxythiophene) (PEDOT) and PANI-PEDOT composite films were electrochemically deposited by potential cycling on indium tin oxide (ITO) modified glass slide (glass/ITO) from a water-based solution. PANI-PEDOT, PANI and PEDOT films were characterized and compared using atomic force microscopy, scanning electron microscopy, electrochemical methods, optical techniques and Raman spectroscopy. Synthesis of PANI in the presence of EDOT allowed to improve conductivity of the deposited film. A charge diffusion coefficient of PANI and PANI-PEDOT films was estimated to be 4.7 x 10(-)(10) and 2.1 x 10(-8) cm(2) s(-1). PEDOT, PANI and PANI-PEDOT (aniline and EDOT monomers ratio 20:1) conductivity values calculated from electrochemical impedance spectroscopy measurements were equal to 1.8 x 10(-6), 2.3 x 10(-9) and 3.3 x 10(-7) S m(-1), respectively. The position of absorption peaks maximum of PANI-PEDOT film can be controlled by changing the concentration ratio of aniline and EDOT. Absorption peaks at 602 and 895 nm tended to shift toward the shorter wavelength region when initial aniline concentration was reduced. The pH sensing capability of PANI-PEDOT film, which was based on changes in optical absorption spectra, was evaluated. Absorption at the maximum of the three peaks (448, 602 and 895 nm) of PANI-PEDOT film depended linearly on the solution pH value in the range from 3.8 to 7.4. Electrochemically deposited PANIPEDOT film was 6.6 times thicker than PANI film (496 +/- 14 vs 75 +/- 2 nm) deposited under similar electrochemical conditions, but despite this the response time of PANI-PEDOT film was 6 times shorter. Therefore, glass/ITO/PANIPEDOT structure could be applied in the design of pH sensors and/or some gas (e.g. CO2 and/or NH3) sensors.