[en] The stage of disease in patients with malignant lymphoma in important in decision of treatment modality and in prediction of prognosis. The authors evaluated the usefulness of PET with F18-FDG in initial staging, in reevaluation after radical therapy and in diagnosis of recurrence or disease progression of malignant lymphoma, compared with conventional imaging studies. The efficacy of positron emission tomography (PET) with fluorine-18-fluorodeoxyglucose (F18-FDG) was evaluated in several tumors. In malignant lymphoma. It was reported that the concentration of FDG was increased in tumor tissues, and that PET with F18-FDG was more sensitive and specific in staging evaluation compared with CT scan. The visual analysis of FDG-PET would be helpful in initial staging work-up, in reevaluation of residual disease after radical therapy and in suspicious recurrence or disease progression, determining the residual disease of lymphoma after radical therapy. But more studies with larger number of cases and longer follow-up were required. The results of this study can be bases for the direction of future studies for the usefulness of PET in malignant lymphoma