Geological mapping is one of the fundamental acts that a geologist should perform in order to proceed to higher levels of a research. This includes basically, mapping of lithological units and tectonic lines (faults). Satellite images give geologists a unique opportunity to observe the complex interaction of large-scale geological structures that make up Earth's landscape. Furthermore, digital satellite data can be manipulated and enhanced in order to accentuate the surface expressions of certain geological features. In most of the cases, this is usually done in “ideal” test sites, with absence of vegetation, soil cover, etc. In this paper, various digital image processing techniques were applied on Landsat-7/ETM+ and Terra/ASTER satellite images, acquired on different dates, in order to produce the most appropriate images for geological mapping, in typical Mediterranean terrain. Two areas were chosen as case studies, the Kassandra peninsula and Thassos island. Boundaries of photo-lithological units and photo-lineaments are drawn on the above satellite images. The results are compared with digitized geological maps of 1/50.000 scale and are evaluated.