Modern space borne SAR sensors provide geometric resolution of one meter. Airborne systems acquire imagery with even higher resolution. In data of this kind many features of urban objects become visible, which were beyond the scope of radar remote sensing only a few years ago. However, layover and occlusion issues inevitably arise in undulated terrain and urban areas because of the side-looking SAR sensor principle. In order to support interpretation, SAR data can be analyzed using additional complementary information provided by optical data. The focus of this paper is on building extraction in urban scenes by means of combined SAR data and optical aerial imagery.