Series of samples of lightly Ga-doped CdO thin films (3%, 6%, and 9%) have been prepared by evaporation method on glass substrate. The prepared films were characterised by X-ray diffraction (XRD), UV - VIS - NIR absorption spectroscopy, and dc-electrical measurements. The investigation shows that Ga doping widens the energygap of CdO. The optical properties were easily explained by using Tauc et al. hand-to-hand transitions and classical Drude theory. The electrical behaviour of the samples shows that they are degenerate semiconductors. The 6% Ga-doped CdO sample shows increase its mobility by 3.2 times, increase its conductivity by 1.5 times, increase its intrinsic bandgap, and a slight increase its transmittance relative to undoped CdO film. Explanation was given concerning these variations. From transparent conducting oxide (TCO) point of view, Ga is not sufficiently effective for CdO doping comparing to other dopants like In, Sn, Sc, and Y. (c) 2007 Published by Elsevier Ltd.