This was an observational study so participants only took medication that was prescribed by their regular healthcare provider. No additional study medication was administered. This study enrolled patients who were previously diagnosed with moderate to very severe chronic obstructive pulmonary disease (COPD). This study looked at the prevalence of chronic bronchitis in patients suffering from moderate, severe or very severe COPD, and it also compared worsening of COPD in patients with or without chronic bronchitis. This study enrolled 976 patients. This multi-centre trial was conducted in Belgium and Luxembourg. The overall time to participate in this study was at a single, regularly scheduled visit at the pulmonologists office. There were no follow-up assessments for this study.