Malignant lymphomas represent a diverse range of diseases with exceedingly different behaviour. The common clinical denominator, however, is necessary for correct staging and reliable monitoring of therapy. Many reports on the usefulness of 18F-fluoro-deoxy-glucose positron emission tomography (18F-FDG-PET) in staging and follow-up of lymphomas have been published with very promising results. The aim of this review was to highlight the impact of 18F-FDG-PET with respect to the distinct lymphoma entities. The possible future role of PET/computed tomography (CT) is tersely mentioned. Reviewing the literature regarding 18F-FDG-PET according to the WHO classification of lymphomas found the method to be highly reliable in Hodgkin's lymphoma (HL), and especially useful in therapy monitoring in HL patients. Promising data have also been published on follicular lymphoma in spite of its indolent nature, and for the aggressive diffuse large B-cell lymphoma 18F-FDG-PET should be considered standard in assessment of response. For marginal zone lymphoma, especially its common extranodal variant (mucosa-associated lymphoid tissue lymphoma) 18F-FDG-PET results are varying, and the method cannot be recommended for uncritical widespread use in the clinical practice. For the less common lymphoma entities, only few results could be found, but they were nevertheless promising for mantle cell lymphoma (MCL). More mature data are nevertheless still needed to judge the use of 18F-FDG-PET in MCL.