The strategy of the initial treatment in patients with lymphoma is based on the determination of the histological subtype, pretreatment identification of risk factors and precise disease staging. Staging of the lymphoproliferative process has classically been carried out based on bone marrow biopsy and CT with intravenous contrast. However, in the last decade, 18F-FDG-PET/CT has demonstrated a better diagnostic yield to detect lymph node and extra lymph node involvement prior to treatment, allowing more correct staging of lymphomas according to the Ann Arbor classification with the Cotswolds modification. PET/CT has greater sensitivity for sites of extranodal involvement a correspondingly has been found to improve baseline staging compared with conventional staging with CT alone. PET/CT findings also can indicate the overall level of metabolic activity of lymphoma, which correlates with level of aggressiveness and with LDH level (a prognostic predictor). In general, indolent follicular lymphoma is associated with low-grade FDG uptake and a low LDH level, whereas higher intensities of FDG uptake are seen in more aggressive lymphoma with higher LDH levels. On comparing PET/CT with conventional CT in the staging of the subtypes of lymphomas mentioned, a sensitivity of 94% vs. 88% and a specificity of 100% vs. 86% have been reported, respectively, thereby demonstrating greater precision of the functional study due to the presence of lesions with metabolic alterations which do not yet present radiological manifestations. Systematic staging of lymphoma should include the following: description of nodal stations involved; representative uni-linear measurements of enlarged lymph nodes in the long axis; identification of sites of extranodal involvement; and detection of coexisting abnormalities that can affect management, such as infection in the lungs and facial sinuses and incidental pathologic and malignant changes