Landsat MSS and SIR-A data have been used in the geological study of the Central Baluchistan mountains in Pakistan. The two show both significant similarities and differences. In terms of interpretable images the SIR-A imagery allows better delineation of various rock units. High radiometric radar backscatter enhances surface textures, relief, moisture conditions, land use patterns and abandoned channels in favourable conditions. A number of geological structures including faults, folds and major and minor lineaments were identified on both images. However, structural lineaments were well expressed on radar with the exception of those parallel or sub-parallel to the direction of illumination. Drainage networks in mountainous terrains have been accurately delineated on Landsat but not on radar imagery, whereas more information on drainage in flat areas was extractable from the radar data. Moisture content variations in the surficial deposits were delineated better on SIR-A than on Landsat data.