PURPOSE: The purpose of this study was to identify factors that influence the functional status of chronic lung disease patients. METHOD: A descriptive, correlational study design was used. The study was conducted at the outpatient respiratory clinic of the large university hospital in Korea. A convenience sample of 128 chronic lung patients (age = 64.2 yrs; 106 COPD, 17 bronchiectasis, 5 DILD) with mean FEV1 64.4 % predicted. Functional status was measured with SIP. Physical variables (FEV1% predicted, dyspnea, fatigue, pulmonary symptom distress), psychological variables (mood, stress), and situational variable (sleep quality) were examined. Dyspnea was measured by the BDI, fatigue was measured with the MFI. Mood was measured with the modified Korean version of POMS. Sleep quality was measured with the Pittsburgh Sleep Quality Index. Potential independent variables for the regression were age, gender, years since diagnosis, FEV1% predicted, dyspnea, fatigue, pulmonary symptom distress, stress, and sleep quality. RESULT: In general, functional status was relatively good. In regression analysis, functional status were significantly influenced by dyspnea, mood, age and fatigue. These variables explained 70 % of the variances in functional status. CONCLUSION: The results suggest that psychophysiologic symptom management should be a focus to enhance the functional status in this group.