Polycrystalline CdTe films have been thermally deposited on quartz substrates under different conditions. The reflectance and transmittance have been measured at normal incidence, and the complex refractive index has been determined in the spectral range 0.4-3.0 mu m. The accuracy of the adopted technique has been analyzed, and has been found to be +/-1.0% and +/-0.5% for the real refractive index n and extinction coefficient k respectively. The effect of the deposition conditions on the optical parameters has been studied separately. The results showed thickness-dependent and substrate temperature-dependent properties, while it was not possible to find any correlation with the rate of deposition. An interpretation of the results, in correlation with corresponding microstructural parameters, the internal microstrain and crystallite size, is presented.