Background It has been reported that B cell activating factor belonging to the tumor necrosis factor family (BAFF) expression is increased in chronic obstructive pulmonary disease (COPD). However its role in this chronic inflammatory disease is not fully understood. Previous studies have suggested that BAFF also affects T cell function. We therefore investigated the effects of BAFF on T lymphocytes in COPD. Methods BAFF was detected in the cells of sputum and the plasma. Peripheral blood mononuclear cells (PBMCs) were isolated from COPD patients and treated with BAFF or BAFF plus BR3-Fc (BAFF antagonist). The apoptosis of CD4(+) cells and CD8(+) cells was analyzed by flow cytometry. CD4(+) cells and CD8(+) cells were isolated from peripheral blood of COPD patients respectively and treated with BAFF or BAFF plus BR3-Fc. Interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) were detected in the CD4(+) cells, and perforin and granzyme B were detected in the CD8(+) cells. Results BAFF expression was increased in the cells of sputum and the plasma from COPD patients compared with control subjects. The plasma BAFF levels were inversely correlated with FEV1 percentage of predicted in patients with COPD. BAFF did not significantly alter the apoptosis of CD4(+) cells, however it significantly inhibited the apoptosis of CD8(+) cells from COPD patients. BAFF increased IFN-gamma expression in the CD4(+) cells from COPD patients, while it did not significantly alter the expresson of IL-4 in these cells. BAFF increased the expression of perforin and granzyme B in the CD8(+) cells from COPD patients. Conclusions Our findings indicate that BAFF may be involved in the inflammatory response in COPD via affecting T lymphocytes, suggesting a possible role of BAFF in the pathogenesis of COPD.