The purpose of this study is to determine whether roflumilast is effective in the treatment of exacerbations 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 chest x-ray dated a maximum of 6 months prior to study baseline or a willingness to have a chest x-ray performed at 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