Positron emission tomography has developed very much since the start in the late 1970s, especially with the development of new labelling procedures for PET-tracers. With the development of whole body imaging and the discovery that 18F-FDG allows a high sensitivity for the detection of soft tissue tumors, the clinical use has increased remarkably. The cost-effectiveness of this modality, when properly used, has been demonstrated and 18F-FDG-PET should be considered as an early alternative in patient evaluation.