Lymphoma involvement of the peripheral nerves is a rare clinical presentation of non-Hodgkin lymphoma. We report the case of a 59-year-old woman with the defect of peripheral motor neuron admitted for PET/CT scan. The scan disclosed increased (18)F-FDG activity along the brachial and lumbar plexuses together with very intense (18)F-FDG uptake in the cervical lymph node masses. The diagnosis, based on the subsequent histopathologic lymph node examination, was diffuse large B-cell lymphoma.