Cadmium sulphide (CdS) doped tin oxide (SnO2) thick film sensors is fabricated using screen printing technology for the detection of acetone and liquid petroleum gas. Undoped tin oxide paste prepared using ball mixing and then screen-printed on alumina substrate (sensor S1). Further, we fabricated a 2wt% CdS doped tin oxide thick film sensor (sensor S2) in the laboratory following mixing, firing and other treatment as applied in undoped paste. The fabricated undoped (SnO2) and doped (CdS-SnO2) thick films are characterized using XRD and atomic force microscope (AFM). It is found from XRD analysis that the crystallite size decreases with CdS content and it is 17 nm and 12 nm for undoped and 2wt% CdS doped SnO2 respectively. The grain size was about 75 nm and 46 nm for undoped and CdS doped tin oxide thick films were obtained by AFM investigation. The sensing response of the fabricated sensor (S1, S2) is measured with varying concentration (0-5000 ppm) of acetone and LPG in air ambient at 200 0C. Measurement reveals that the S2 sensor is more suitable for the detection of acetone over LPG.