FDG uptake refers to the amount of radiotracer uptake in a PET scan. FDG stands for 18F-fluorodeoxyglucose, which is a glucose analogue that is actively transported across the blood-brain barrier and phosphorylated within cells. FDG uptake reflects the tissues metabolic activity, and it is often used to detect cancerous cells in the body. However, not all FDG uptake is abnormal, and it can be reduced in small volume disease due to partial volume effects or in areas subject to movement, mainly due to respiration. The interpreting radiologist must take into consideration any findings on CT, MRI, or other imaging tests when determining what FDG uptake is indicative of. A PET scan report will also indicate SUV (standardized uptake value), which is a measure of the amount of FDG uptake in a particular area of the body. While it is natural to believe that higher SUV values indicate cancer, this is not always the case, and recognition of aggressive lesions that are not FDG-avid, and intensely FDG-avid but benign pathologies is essential.