Nanocrystalline semiconducting devices have wide range of applications such as optical mass memories, sensors, etc. Present research work is related to the quantum size effects observed in chemically deposited Sb2S3 thin films. Preparative parameters such as volume ratio, pH, temperature are optimized at room temperature. By keeping fixed preparative parameters, deposition was carried out at 6(+/-2) degreesC for different deposition time periods (4-20 h). Effects of thickness and/or grain size of chemically deposited Sb2S3 films on structural, optical, electrical properties have been studied by using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), d.c. two point probe method techniques, respectively. The decrease in the bandgap, energy from 2.16 to 1.86 eV with increase in thickness 77-206 nm implies existence of quantum size effect as it reveals broadening of energy band with decreasing grain size. Change in thickness increases grain size, which is evidenced by XRD and SEM studies. AFM photograph gives evidence that the deposited films are nanocrystalline and shows n-type behavior as conformed from the sign of developed thermo-emf. (C) 2003 Elsevier B.V. All rights reserved.