Abstract: Using electrochemical deposition of tungsten oxide from a metastable acidic solution of isopolytungstates into a poly(3,4-ethylenedioxithiophene) film, composite films were obtained on optically transparent electrodes made of fluorine-doped tin oxide on glass. In situ electronic spectra of poly(3,4-ethylenedioxithiophene)–tungsten oxide composite films and their components, poly(3,4-ethylenedioxithiophene) and tungsten oxide films, were studied using the spectroelectrochemistry method at various electrode potentials. The good additivity of the spectra of the composite and its constituent components suggests that there is no pronounced specific chemical interaction between the components, except for the electrostatic interaction between positively charged polymer fragments and negatively charged polymer oxo anions of tungsten oxide.