Over the last 20 years, PET (positron emission tomography) and PET/CT (positron emission tomography/computed tomography) have revolutionized the care of cancer patients. It is one of the fields in medical imaging with the highest growth rate. Proper cancer management requires highly accurate imaging in order to select the correct treatment that applies to the individual patient. The ability to provide, in a single imaging session, detailed anatomical and metabolic/functional information, has established PET/CT as an indispensable imaging procedure in the management of many types of cancer. The reliability of the images acquired on a PET/CT scanner depends on the quality of the imaging technique. This publication addresses an important aspect of PET/CT imaging, namely how to perform the fluorine-18-FDG PET/CT scan in an adult patient with cancer.