The role of tumor-infiltrating T cell subsets in the prognosis of non-Hodgkin's lymphoma (NHL) has previously been reported. In the present study, we investigated the prognostic significance of different T cell subsets in the peripheral blood of NHL patients. Immunophenotyping was performed on the peripheral blood samples of 45 patients with newly diagnosed B cell NHL using flow cytometry. The relationship between T cell subsets of CD4+, CD8+, CD3+CD25+, CD4+CD25+, CD4+CD25high [as T regulatory cells (T reg)], and the CD4/CD8 ratio with international prognostic index (IPI) and response to therapy was determined. The percentages of CD3+, CD4+, and CD8+ T cells in the peripheral blood of the patients were 49.1±20.3%, 23.6±11%, and 31.4±14.4%, respectively (CD4/CD8 ratio: 0.92±0.6). There were 4.2±3.2% T reg cells. A study of the percentage of T cells in relation to IPI score showed a higher proportion of CD3+CD25+, CD4+, and CD4+CD25+ cells in low-risk patients compared with intermediate/high risk groups (p<0.05). The above cells, as well as CD4+CD25high T reg cells, indicated a positive correlation with complete remission (CR) and survival. CD4 positivity correlated significantly with survival and CR durations, which were longer in patients with ≥20% CD4+ cells than those with <20% CD4+ cells, thus indicating the prognostic value of CD4+ T cells in NHL patients. There was no significant data on CD8+ cells as well as the CD4/CD8 ratio between distinct IPI groups and response to therapy. These data indicated the importance of CD4+ cells and the activation status of T cells in immunity against lymphoma and the prognostic implication of enumeration of these cells in NHL patients.