Thin films of CdS0.9Se0.1:ln (0.05 mol%) of various thicknesses have been deposited on to the clean glass substrates using a chemical deposition technique. Composition analysis showed that films were sulphur deficit. Structural investigations on these films revealed the polycrystalline nature of the films with the presence of hexagonal CdS0.9Se0.1 and cubic CdS phases. Grain size increased with the film thickness. Electrical conductivity and thermoelectric power (TEP) measurements have been carried out in 300-550 K temperature range. The conduction activation energy is found to be thickness-dependent, TEP measurements showed n-type conduction. Carrier concentration increased with thickness.