Patients will be randomized (1 to 1 ratio) to a 4-week double-blind treatment period of either FDC of tiotropium + olodaterol (5/5 µg) plus placebo or the free combination of tiotropium 5 µg and olodaterol 5 µg; all administered via the Respimat® inhaler. The purpose is to show non-inferiority between the FDC and the free combination of tiotropium and olodaterol in patients with COPD.