Highly crystalline CdS films were deposited by an ammonia-free chemical bath deposition process which uses amino acids as complexing agents. All films have shown the hexagonal (wurzite) structure with preferential orientation in the plane (002). As consequence of the difference in the stability between the Cd-glycine and Cd-alanine complexes, CdS films with different thicknesses were obtained. The band gap energy values of the resulting films were at the range of 2.43 to 2.52 eV. (C) 2016 Elsevier B.V. All rights reserved.