Radar remote sensing has a significant role in remote sensing technologies and develops rapidly. A series of new synthetic aperture radar (SAR) satellites has been launched to space having various operation modes which offer different resolutions and advantages. A very actual SAR satellite is German TerraSAR-X (TSX), launched on 15th June 2007. This satellite is a revolution for the SAR technologies at the resolution side and offers 1m ground resolution in Spotlight mode. To investigate the quality of digital surface models (DSM) which are derived from high resolution data of this satellite, a comparison has been made to a DSM based on optical space images taken by IKONOS. For the test DSMs have been generated with the SAR and the optical data covering parts of Istanbul, Turkey and are compared with a more accurate DEM of same area, based on aerial photogrammetry. This was leading to the result, that the high resolution Spotlight mode TSX model has nearly the same visual quality and absolute accuracy as the IKONOS model and has a slightly better relative accuracy.