Positron emission tomography (PET) with 2-[¹⁸F]fluoro-2-deoxy-D- glucose (FDG) is a noninvasive imaging technique that provides a fundamental advantage by allowing the functional characterization of lymphoma tissue via the detection of increased glycolysis, which is a typical sign for an active tumor. Whole-body FDG-PET generates tomographic images of the entire patient and shows the distribution of FDG throughout the body. There is growing evidence that FDG-PET is more accurate in the staging of lymphoma patients compared with conventional staging procedures. Several investigators have shown the potential of FDG-PET in the nodal staging, in the detection of extranodal lymphoma, as well as for bone marrow involvement. In lymphoma patients with residual masses after treatment, a negative PET result was associated with a high chance of complete remission. A whole-body FDG-PET- based staging and follow-up algorithm may be an accurate and cost-effective method for monitoring lymphoma. In the future, immunoscintigraphic studies using FDG-PET with radiolabeled monoclonal antibodies and studies on the pharmacokinetics of cytostatic will follow, especially on the background of future treatments, such as gene therapy.