The ZincPhthalocyanine (ZnPc) thin films were obtained by thermal evaporation method. The X-ray diffraction analysis of vacuum evaporated ZnPc films reveals that the structure of the film is polycrystalline in nature for the samples grown at higher substrate temperatures. The crystallite size (D), dislocation density (delta) and strain (epsilon) were calculated. The optical band gap energy has been calculated from the (alphahv)(2) vs. hv plot. The optical band gap energy of the ZnPc films was found to decrease with increase in film thickness. (C) 2004 Elsevier B.V. All rights reserved.