The effect of film thickness on optical properties of the Cr(III) complex having 2-pyridincarbaldehye thiosemicarbazone thin films was investigated. The analyses of the optical absorption data revealed existence of direct and indirect transitions in the optical band gap. The optical constants (refractive index and dielectric constant) of the thin films were determined. The thickness of the films causes important changes in refractive index and real part-imaginary parts of the dielectric constant. The most significant result of the present study is to indicate that thickness of the film can be used to modify in the optical band gaps and optical constant of the thin films. (c) 2004 Elsevier B.V. All rights reserved.