An 82-year-old man received right upper lobectomy for lung cancer in April 2006. In August, 2006, he was readmitted to our hospital due to left cervical and left inguinal lymph node swelling. A pathologic diagnosis of diffuse large B-cell lymphoma (DLBCL) was made from a biopsy specimen of the left cervical lymph node. The immunophenotype of the lymphoma cells was CD2-, sCD3-, cCD3-, CD4+, CD5+, CD7-, CD8-, CD10-, CD19+, CD20+, CD23+, CD25+, kappa+, lambda-, CD56-, and dual staining confirmed that the cells were positive for both CD4 and CD19. From these findings, he was diagnosed with CD4-positive DLBCL. Five cycles of R-CHOP were performed and complete remission was achieved. To our knowledge, this is the first report of CD4-positive DLBCL.