ZnO thin films were prepared using zinc chloride, zinc acetate and zinc nitrate precursors by spray pyrolysis technique oil glass substrates at 550 degrees C. Structural and optical properties of ZnO films were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and optical transmittance spectra. Regardless of precursors, ZnO thin films are all in hexagonal crystallographic phase and have to (0 0 2) preferred orientation. SEM images show completely different surface morphologies for each precursor in ZnO thin films. ZnO rod was observed only for zinc chloride precursor. The optical measurements reveal that films have a low transmittance and a direct band gap approximately 3.30 eV, which is very close to band gap of intrinsic ZnO. (C) 2007 Elsevier B.V. All rights reserved.