Cd1-xZnxSe (x = 0, 0.5 and 1) thin films have been deposited onto glass substrates using thermal evaporation technique. The lattice constants, grain size, microstrain and dislocation density were studied by using X-ray diffraction. In addition the optical constants were calculated in the wavelength range 400-2500 nm. Transmittance and reflectance were used to calculate the absorption coefficient alpha and the optical band gap E-g. The linear relation of (alpha h upsilon)(2) as a function of photon energy h upsilon for the thin films illustrated that the films exhibit a direct band gap, which increases with increasing Zn content. This increasing of optical band gap was interpreted in accordance to the increasing in the cohesive energy. Optical constants, such as refractive index n, optical conductivity sigma(opt,) complex dielectric constant, relaxation time tau and dissipation factor tan delta were determined. The optical dispersion parameters E-0, E-d were determined according to Wemple and Di Domenico method. (C) 2012 Elsevier B.V. All rights reserved.