F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) imaging is being increasingly utilized in the detection of malignancy and in following the effects of therapy. FDG-PET imaging has been demonstrated to be accurate in the diagnosis of several malignancies including lung cancer, lymphoma, recurrent colorectal cancer, and recurrent melanoma. The initial studies evaluating FDG-PET in determining the effect of therapy reveal promising results. The clinical images are interpreted subjectively like other clinical nuclear medicine imaging studies. Semiquantitative indices such as the standardized uptake value may be used for research purposes to provide a quantitative parameter from the study.