Main Inclusion Criteria:

• Written informed consent
• Patients with a history of chronic obstructive pulmonary disease for at least 12 months as defined by the GOLD (Global Initiative on Obstructive Lung Diseases) criteria (2003)
• Age ≥ 40 years
• FEV1/FVC ratio (post-bronchodilator) ≤ 70%
• FEV1 (post-bronchodilator) ≤ 65% of predicted
• FRC (post-bronchodilator) ≤ 120% of predicted
• Clinically stable COPD within 4 weeks prior to baseline visit (B0).
• 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 at visit (B0).

Main Exclusion Criteria:

• COPD exacerbation indicated by a treatment with systemic glucocorticosteroids not stopped at least 4 weeks prior to the baseline visit (B0)
• Non smoker, current smoker or ex-smoker (smoking cessation at least one year ago) with a smoking history of < 10 pack years
• Suffering from any concomitant disease that might interfere with study procedures or evaluation
• Lower respiratory tract infection not resolved 4 weeks prior to the baseline visit (B0)
• Diagnosis of asthma and/or other relevant lung disease (e.g. history of bronchiectasis, cystic fibrosis, bronchiolitis, lung resection, lung cancer, interstitial lung disease [e.g. fibrosis, silicosis, sarcoidosis], and active tuberculosis)
• Current participation in a pulmonary rehabilitation program or completion of a pulmonary rehabilitation program within 2 months preceding the baseline visit (B0).
• Known alpha-1-antitrypsin deficiency
• Need for long term oxygen therapy defined as ≥ 15 hours/day
• Clinically relevant abnormal laboratory values suggesting an unknown disease and requiring further clinical evaluation (as assessed by the investigator)
• Known infection with HIV, active hepatitis and/or liver insufficiency
• Diagnosis or history of cancer (other than basal cell carcinoma) or recurrence within 5 years prior to study start
• Clinically significant cardiopulmonary abnormalities (diagnosed clinically or by x-ray/ECG) that are not related to COPD and that require further evaluation
• Pregnancy, breast feeding, oocyte donation or oocyte implantation planned during the trial
• The female patient is of childbearing potential and is not using and is not willing to continue to use a medically reliable method of contraception for the entire study duration, such as oral, injectable, or implantable contraceptives, or intrauterine contraceptive devices, unless she is surgically sterilized/hysterectomized or post-menopausal > 1 year or any other criteria considered sufficiently reliable by the investigator in individual cases
• Participation in another study (use of investigational product) within 30 days preceding the baseline visit (B0) or re-entry of patients already enrolled in this trial
• Suspected inability or unwillingness to comply with study procedures
• Alcohol or drug abuse
• Inability to follow study procedures due to, for example, language problems or psychological disorders
• Use of prohibited drugs
• Suspected hypersensitivity to the study medication and/or contraindication to any ingredients of the study medication (roflumilast) or rescue medication