Diffuse large B cell lymphoma (DLBCL) cells can be sub-classified into germinal center B cells (GCB) and non-GCB immunophenotypes. In the present study, we treated 161 newly diagnosed DLBCL patients with cyclophosphamide, epirubicin, vincristine, and prednisolone (CEOP) regimen with or without rituximab, and retrospectively investigated DLBCL sub-classifications combined with assessment of B cell lymphoma 2 (Bcl-2) expression level for their utility in the prediction of clinical efficacy. Survival analyses showed that non-GCB patients treated with R-CEOP regimen had significantly higher 5-year OS rates than the CEOP group (P = 0.033), while no statistically significant difference was observed between R-CEOP and CEOP treatments in GCB patients (P = 0.317). Prognosis was poorest for high Bcl-2 expressing non-GCB subgroup patients treated with CEOP, compared with Bcl-2 negative non-GCB CEOP patients (P = 0.044). In the R-CEOP group, Bcl-2 expression had no significant effect on prognosis for both GCB and non-GCB patients. The addition of rituximab to CEOP chemotherapy negates the adverse prognostic influence of Bcl-2 protein expression on overall survival in non-GCB DLBCL.