CdS films were grown by chemical bath deposition. The as-grown films had the cubic CdS crystalline structure. As-grown films were thermally annealed in a controlled atmosphere. The annealing temperature was varied from 200 to . The annealing process produces a gradual structural transition from cubic for the as-grown CdS film to hexagonal for the CdS film annealed at . The CdS structural transition is studied by x-ray diffraction spectroscopy, atomic force microscopy and by optical absorption measurements. The changes in surface morphology, as observed from atomic force three-dimensional images of the as-grown and annealed film surfaces, provide a direct indication of the structural transition performed by the CdS annealed films.