Cadmium oxide (CdO) thin films were electrodeposited on indium doped tin oxide glass substrates from aqueous solution and subsequently annealed at higher temperatures up to 600 degrees C in air, oxygen and inert gas ambients, respectively. The effect of annealing on the morphology, crystalline quality and optical properties of CdO films was investigated. The CdO films were polycrystalline in nature and the grain size strongly depended on the annealing temperature as well as annealing ambient. CdO films were highly transparent in the visible region of the spectrum. The transmittance of the films decreased with increasing annealing temperatures in all the three ambients. Optical bandgap of the nanocrystalline CdO films varied in the range of 2.20-2.54 eV. (C) 2011 Elsevier B.V. All rights reserved.