We retrospectively evaluated (18)fluoro-2-deoxyglucose positron emission tomography (FDG-PET) scans in 172 patients with lymphoma and correlated results with pathologic diagnosis using the World Health Organization (WHO) classification system. In total, FDG-PET detected disease in at least one site in 161 patients (94%) and failed to detect disease in 11 patients (6%). The most frequent lymphoma diagnoses were diffuse large B-cell lymphoma (LBCL; n = 51), Hodgkin lymphoma (HL; n = 47), follicular lymphoma (FL; n = 42), marginal zone lymphoma (MZL; n = 12), mantle cell lymphoma (MCL; n = 7), and peripheral T-cell lymphoma (PTCL; n = 5). FDG-PET detected disease in 100% of patients with LBCL and MCL and in 98% of patients with HL and FL. In contrast, FDG-PET detected disease in only 67% of MZL and 40% of PTCL. Comparison with bone marrow biopsies showed that FDG-PET was not reliable for detection of bone marrow involvement in any lymphoma subtype.