We treated the surface of indium-tin oxide (ITO) substrates in two ways, (i) coating of thin insulating ITO layer or (ii) irradiation of the surface with accelerated ions, and investigated the change in sheet resistance (R-sh) and the water-contact angle (WCA). Rsh increased with the thickness of the insulating ITO layer or with the ion dose. WCA dropped as a result of the surface treatment to < 15degrees. The microstructure, the surface morphology, the optical transmittance, and the stoichiometry of US improved with the surface treatment. CdS/CdTe solar cells showed a better performance as a result of ITO surface treatment. (C) 2002 Published by Elsevier Science B.V.