The role of 2-[fluorine 18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) in combination with computed tomography (CT) in the evaluation of pelvic malignancies has been rapidly growing in recent years. FDG PET has proved to be valuable in the evaluation of a variety of pelvic malignancies, including colorectal cancer, uterine cervical cancer, ovarian cancer, endometrial cancer, and non-Hodgkin lymphoma. However, a number of pitfalls are commonly encountered at FDG PET, including normal physiologic activity in bowel, ovaries, endometrium, and blood vessels and focal retained activity in ureters, bladder diverticula, pelvic kidneys, and urinary diversions. The use of an in-line FDG PET-CT system, with special attention given to proper patient preparation and scanning protocol, often provides valuable information to help localize and define disease and avoid potential diagnostic pitfalls.