Immune cells expressing the activation markers HLA-DR and regulatory T cells (Tregs) may be involved in the regulation of chronic inflammation in chronic obstructive pulmonary disease (COPD). In this study we analyzed native and activated cell profiles in sputum of 22 stable COPD patients receiving formoterol (F) or formoterol + tiotropium (F + T) for 3 months. Cells were isolated from induced sputum and were examined on Coulter flow cytometer using fluorescent antibodies specific for CD3, CD4, CD8, CD14, CD19, CD25, CD127, and HLA-DR antigens. Cell profiles and cell activation were assessed by analysis of HLA-DR, CD25, and CD127 co-expression in double-stained samples. Tregs were defined as CD4⁺CD25(high) CD127(low) cells. We found that the combined therapy significantly decreased the CD8⁺ cell number (p < 0.01). At baseline, HLA-DR was expressed in about 10 % of sputum T or B cells and a higher expression was found on monocytes. The HLA-DR expression on lymphocytes, but not monocytes, was significantly lower (p < 0.01) in patients treated with F + T. Fractions of activated [CD4⁺ CD25⁺] cells were also significantly lower in the combined therapy group, except for the subpopulation of CD4⁺CD25(high) CD127(low) cells which was not altered. We conclude that tiotropium in add-on therapy to formoterol affects Treg cell profiles and decreases HLA-DR expression in airway lymphocytes.