Radiosurgery was already examined as a therapy for surgically inaccessible targets in the head by the Swedish neurosurgeon Lars Leksell back in 1948. Since the development of the GammaKnife System in the 1960s and 1970s, the intracranial radiosurgery has been an integral component of the treatment of benign and malignant tumors and functional disorders. Radiosurgery for areas outside the head has only been researched more broadly with technical improvement of the targeted precision in the late 1990s. This includes the treatment of vertebral, lung, liver and also prostate tumors. When using radiosurgery, high-energy x-rays are directed to the determined target in the body; tumor cells as well as functional disorders can be treated with radiosurgery. Its sophisticated digital image guidance and the robotic control featured by the CyberKnife technology can focus the required high radiation doses with accuracies in the sub-millimetre range, even if the targets (e.g. lung and liver tumors) are moving. Thus, a minimum effect on the healthy organs and a maximum effectiveness in the fight against tumors and functional disorders can be guaranteed.