The purpose of this study is to assess the efficacy (effectiveness) and safety of aclidinium bromide doses as compared to placebo in the treatment of moderate to severe chronic obstructive pulmonary disease. The study will be 16 weeks in duration; 2-week run-in period, 12-week double-blind treatment, and 2-week follow-up phone visit.

Inclusion Criteria:

• A diagnosis of stable moderate to severe COPD as defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines, 2009; postbronchodilator FEV1/FVC < 70%, and postbronchodilator FEV1 ≥ 30% and < 80% predicted
• Current or former cigarette smokers

Exclusion Criteria:

• Patients who have been hospitalized for an acute COPD exacerbation within 3 months before the first visit
• Respiratory tract infection or COPD exacerbation in the 6 weeks before Visit 1
• Patient with any clinically significant respiratory conditions other than COPD, cardiovascular conditions or mental illness
• History or presence of asthma verified from medical records
• Chronic use of oxygen therapy greater than or equal to 15 hours per day
• Patient with uncontrolled infection due to HIV and/or active hepatitis
• Patients with a history of hypersensitivity reaction to inhaled anticholinergics
• Patients with clinically significant cardiovascular conditions, including myocardial infarction during the previous 6 months, newly diagnosed arrhythmia within the previous 3 months, unstable angina, unstable arrhythmia that had required changes in pharmacological therapy or other intervention.