Nanostructured zinc oxide thin films were prepared by thermal oxidation of Zn metallic thin films (prepared by PVD method) at various temperatures of 550, 600 and 650 ⁰C in air in a duration time of 1 h. Samples were characterized by SEM images, XRD and UV-vis. spectra. The SEM images showed that with increasing the synthesis temperature the length of ZnO nanowires are increased. Also XRD results demonstrated that all samples have a hexagonal structure, and the crystallite sizes are increased with oxidation temperature. Analysis of the absorbance data showed that with increasing the growth temperature the band gap of the samples are decreased due to the occurrence of the quantum confined effect.