FDG PET is a functional imaging modality whose ability to detect lesions is directly based on a change of the glycolytic metabolism of targeted tissues, may be advantageous over other techniques. Combined with excellent image qualify, high spatial resolution, and whole body imaging capability, it has become popular as a new approach in the evaluation of patients with various malignancies. Initial staging of nodal and extranodal lymphoma using FDG PET has been proven to be at least equal or superior to conventional imaging modalities. For the assessment of treatment responsiveness, FDG PET has a major impact on the management of patients in differentiating residual lymphoma from treatment related benign changes. Residual FDG uptake after the completion of chemotherapy is a good predictor of early relapse. However, it seems that the absence of FDG uptake in tumor mass may not exclude minimal residual disease causing later relapse. In the early evaluation of treatment response only after a few cycles of chemotherapy, FDG PET may have a promising role in identifying non-responders who could benefit from a different treatment strategy. At present, FDG PET appears to be the cost-effective, diagnostic modality of choice in the management of lymphoma patients. The role of FDG PET based-systems in terms of affecting long-term prognosis and survival benefit should be further elucidated in future prospective studios.