Cadmium sulfide (CdS) nanocrystalline thin films were prepared using the microwave-assisted chemical bath deposition method onto glass substrates at 80 degrees C. Aqueous solutions of either cadmium chloride or cadmium acetate and thiourea were used as sources of Cd2+ and S2- ions, respectively. Two sets of samples with different concentrations were prepared. A microwave oven was used as a heating source to synthesize the nanocrystalline CdS thin films. The prepared thin films had a good adhesion with no pinholes. These films were examined for their structural and surface morphologies by X-ray diffraction (XRD), scanning electron microscopy, and atomic force microscopy. The optical properties were investigated using UV-vis spectrophotometer, photoluminescence, and Raman spectroscopy. Particle size values obtained from XRD were compared with these calculated using effective mass models. The values of optical band gaps according to optical transmission measurements decreased as the ion source molar concentration increased. (C) 2011 Elsevier B.V. All rights reserved.