Positron emission tomography (PET) and computed tomography (CT) complement each other’s strengths in integrated PET/CT. Most PET/CT studies in oncology are performed with 18F-fluorodeoxyglucose (FDG). FDG is a glucose analogue that is taken up and trapped within viable cells. An increased glycolytic activity is a characteristic in many types of cancers resulting in avid accumulation of FDG. These tumours excel as “hot spots” in FDG-PET/CT imaging. FDG-PET/CT proved to be of high diagnostic value in staging and restaging of different malignant diseases, such as colorectal cancer, lung cancer, breast cancer, head and neck cancer, malignant lymphomas, and many more.