The aim of the study is to compare the effect of roflumilast on lung function in patients with COPD. Roflumilast will be administered orally once daily in the morning at one dose level. The study duration consists of a baseline period (4 weeks) and a treatment period (12 weeks). The study will provide further data on safety and tolerability of roflumilast.

Main Inclusion Criteria:

• Written informed consent
• Patients with a history of chronic obstructive pulmonary disease (COPD) as defined by the GOLD criteria (2003)
• FEV1/FVC ratio (post bronchodilator) smaller or equal 70%
• FEV1 (post bronchodilator) 30-80% of predicted
• Fixed airway obstruction
• Current smoker or former smoker (smoking cessation at least one year ago) with a smoking history of at least 10 pack years
• Clinically stable COPD within 4 weeks prior to baseline visit
• Availability of a chest x-ray

Main Exclusion Criteria:

• COPD exacerbation indicated by a treatment with systemic glucocorticosteroids
• Lower respiratory tract infection
• Diagnosis of asthma
• Known alpha-1-antitrypsin deficiency
• Need for long term oxygen therapy defined as longer or equal 16 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 (according to the Child Pugh score A or worse)
• Diagnosis or history of cancer
• Clinically significant cardiopulmonary abnormalities
• Pregnancy, breast feeding, oocyte donation or oocyte implantation planned during the trial
• Female patients of childbearing potential, not using reliable method of contraception for the entire study duration, post-menopausal > 1 year or who are not using any other method considered sufficiently reliable by the investigator in individual cases
• Participation in another study (use of investigational product) within 30 days preceding the baseline visit or re-entry of patients already enroled in this trial
• Alcohol or drug abuse
• Inability to follow the study procedures due to e.g., language problems, physiological disorders
• Use of not allowed drugs
• Suspected hypersensitivity to the study medication or rescue medication