A rare primary non-Hodgkin's lymphoma (diffuse large cell) of the spleen developed in a 72-yr-old man who had successful radiotherapy to the right inguinal region for Hodgkin's disease 23 yr ago. Radiologic findings, particularly the 67Ga scintigraphy finding, were very useful in leading to the correct diagnosis of malignant splenic lymphoma, in this case, preoperatively.