This Phase III study seeks to confirm the long-term bronchodilator efficacy and effects on COPD related health status and other secondary parameters as well as the safety of two doses of the combination of aclidinium bromide/formoterol FDC (FDC 400/12 μg and 400/6 μg) compared with aclidinium bromide monotherapy 400 μg, formoterol monotherapy 12 μg and placebo.