Patients with chronic obstructive pulmonary disease (COPD) have significant psychopathology and cognitive impairment. Psychiatric morbidity and cognitive impairment are due to hypoxia, hypercapnia, COPD exacerbation, smoking and brain damage. Psychopathology and cognitive impairment are related to steroid medications, duration and severity of COPD, age, education and occupation. In this research patients with COPD are compared with bronchial asthma and healthy controls.