Health-related quality of life is usually impaired in patients with moderate to severe chronic obstructive pulmonary disease. The Sickness Impact Profile, the Medical Outcome Study "short form" 36, and the Nottingham Health Profile have all been used as generic measures of health-related quality of life. Although the discriminative properties of three disease-specific instruments, the Chronic Respiratory Disease Questionnaire, the St. George's Respiratory Questionnaire, and the Breathing Problems Questionnaire, are similar, the responsiveness of the Chronic Respiratory Disease Questionnaire and the St. George's Respiratory Questionnaire has been the most clearly demonstrated. The characteristics of each instrument should be considered in the selection of specific health-related quality of life questionnaires for clinical research.