Positron emission tomography/computed tomography (PET/CT) is a sensitive method for detecting, staging, and therapy monitoring of many malignancies. It has modified the management of cancer. PET/CT allows for a "whole body" assessment of a metabolic process, depending on the type of tracer, combined with a CT scan. In the present article we review the different PET tracers available today and the most effective applications of PET-CT in oncology, but also in inflammatory diseases, heart diseases and dementia.