Various substrates were compared for the investigation of the optical properties of ZnO thin films. ZnO thin films have been deposited on (I 0 0) p-type silicon substrates and (0 0 I) sapphire substrates by pulsed laser deposition (PLD) technique using a Nd:YAG laser with the wavelength of 355 nm. Oxygen was used as ambient gas. Substrate temperatures were varied in the range of 200-600 degreesC at a fixed oxygen gas pressure of 350 mTorr. We have investigated substrate effect on the optical and structural properties of ZnO thin films using X-ray diffraction (XRD) and photoluminescence (PL).