Objective To explore the clinical characteristics of chronic obstructive pulmonary disease (COPD)in the patients with pulmonary interstitial fibrosis.Methods Twenty-seven COPD patients with pulmonary fibrosis and thirty patients with COPD who were diagnosed from July 2001 to October 2010 were analyzed for their clinical symptoms,physical signs,pulmonary function,arterial blood-gas,radiographic features,CT and high resolution computed tomography(HRCT)of the chest.Results The clinical features of COPD with pulmonary fibrosis shared that of the two diseases.Eighteen cases of COPD with pulmonary fibrosis had mixed ventilatory dysfunction(P ＜ 0.01).COPD were all obstructive ventilatory dysfunction(P ＜ 0.01).For arterial blood-gas test,PF-COPD showed progressing hypoxemia and little PaCO2 retention,but no significant difference was observed.Chest X-ray showed that 30 cases in the COPD group had an increased anteroposterior diameter of the thorax,while it was 14 cases in the PF-COPD group(P ＜0.05).Twenty four cases in the PF-COPD group showed nodular,meshy or honeycomb-like lesions,but none in COPD group(P ＜ 0.01).Chest CT and HRCT showed that there were higher chances of frosted glass-like and grid-like nodular lesions in the lungs of PF-COPD group than in COPD group(9 vs.0,19 vs.0 ;x2 =10.85,17.36,P ＜ 0.01).Conclusions Patients with chronic obstructive pulmonary disease and pulmonary fibrosis sharing the clinical features of both diseases.Chest HRCT can provide important information for clinical diagnosis.