Mature T cell lymphoma has been noted for poor prognosis when compared with B cell lymphoma, even in the pre-rituximab era. To confirm this difference, a retrospective cohort study was conducted. One hundred-and nineteen patients with mature T cell lymphoma and 568 patients with diffuse large B cell lymphoma (DLBCL) who did not receive rituximab as first induction were studied. Overall survival (OS) was worse for patients with international prognostic index (IPI) scores indicating low-risk mature T cell lymphoma than for those with DLBCL (3-year OS 87 % vs. 58 %, P = 0.001), but not in other risk groups. Prognosis of mature T cell lymphoma was significantly poorer in the IPI low-risk group, as compared with DLBCL.