The purpose of this study is to investigate the effect of 500mcg roflumilast vs placebo on exacerbation rate and pulmonary function as well as quality of life in patients with chronic obstructive pulmonary disease (COPD).

Main Inclusion Criteria:

• FEV1/FVC ratio (post-bronchodilator) ≤70%
• FEV1 (post-bronchodilator) ≤50% of predicted
• Current smoker or ex-smoker
• Clinically stable COPD indicated by no exacerbation and no change in COPD treatment of within 4 weeks prior to baseline
• Availability of a chest x-ray dated a maximum of 6 months prior to study baseline visit B0 or a willingness to have a chest x-ray performed before baseline

Main Exclusion Criteria:

• COPD exacerbation indicated by a treatment with systemic glucocorticoids not stopped 4 weeks prior to baseline
• Lower respiratory tract infection not resolved 4 weeks prior to baseline
• Diagnosis of asthma and/or other relevant lung disease
• Known alpha-1-antitrypsin deficiency
• Need for long-term oxygen therapy defined as ≥16 hours/day