Recent research using questionnaire measures has demonstrated high prevalence rates of mental disorders in chronic obstructive pulmonary disease (COPD). However, clinical interviews and clinical rather than healthy control groups have rarely been employed. The aim of the present study was to assess mental disorders in patients with COPD with advanced methodology, to identify moderating factors explaining mental co-morbidities and to compare results with a clinical control group without COPD. A standardized clinical interview (F-DIPS) and a range of questionnaires were used to assess mental disorders, perceived physical symptoms and cognitions in 20 hospitalized patients with mild-to-moderate COPD (mean FEV(1)/VC (%)=61.3). Results were compared with a hospitalized clinical control group without pulmonary dysfunction (CCG; N=20). Results showed that 55% of patients with COPD received a diagnosis of a mental disorder compared to 30% of CCG patients. All principal mental diagnoses in the COPD group were anxiety disorders (especially Panic Disorder with Agoraphobia), while CCG patients received a wider range of diagnoses (anxiety, pain, alcohol abuse). There was no systematic association between anxiety levels and respiratory function in the whole COPD group, but a positive correlation between anxiety levels and perceived physical symptoms (p<0.001) as well as negative cognitions (p<0.001 and p<0.05, respectively) for COPD patients with anxiety disorder (N=11). The present results confirm the high prevalence rate of anxiety in patients with COPD and suggest further that anxiety in COPD patients may be mediated by cognitive processes. These findings are discussed in terms of their implications for treatment.