Abstract The successful commissioning of the XMM-Newton focal plane detectors, radiation hard X-ray imaging spectroscopic CCDs, has attracted some attention: Reliably operating X-ray CCDs are delivering extraordinary images, recorded in a single-photon counting mode, imaged through the largest X-ray telescope ever built. The experimental boundary conditions from space applications will serve as a setting to confine the scope of this review. Of course, related applications in other fields of basic and applied science will also be treated. State of the art X-ray detectors with energy, position and time resolution at high quantum efficiency from the near-infrared up to 20 keV are described in detail: todays most advanced systems comprise charge coupled devices and active pixel sensors as well as pixellized silicon drift detectors. They have been developed for astrophysics experiments in space, for material analysis and for experiments at synchrotron radiation facilities. The functional principles of the silicon devices are derived from basic solid-state device physics. The spatial resolution, the spectroscopic performance of the systems, the long-term stability and the limitations of the detectors are described in detail. Field applications show the unique usefullness of silicon radiation detectors.