Objective To investigate the clinical manifestations of two common obstructive airway inflammatory diseases [ chronic obstructive pulmonary disease ( COPD) and asthma] in elderly patients for proper diagnosis and treatment of COPD complicated with asthma.Methods 102 elderly patients diagnosed with either COPD or asthma, who visited the Guangzhou Institute of Respiratory Disease fromOctober 2010 to March 2011, were recruited for the study. Comparisons of clinical manifestation, pulmonary function tests ( PFTs) , chest CT and sputum cytological tests were carried out between the patients with asthma-only,COPD-only, and COPD complicated with asthma. Results Of all 102 patients,18 were diagnosed as asthmaonly ( 17. 6% ) , 36 as COPD complicated with asthma ( 35. 3%) , and 48 as COPD-only ( 47. 1% ) . The patients with COPD-only had longer history of present illness in which most had a history of exposure to cigarette smoking. 91. 7% complained of cough as the first symptom, 80% showed severe impairment in PFTs. Among these patients, sputum neutrophilic granulocytes were ( 78. 3 ±5. 1) % , which was significantly higher than the other two groups ( P lt; 0. 05) . Glucocorticosteroid treatment was less effective in thesepatients. In the patients with COPD complicated with asthma, half were smokers, and cough was the first symptom in 63. 9% subjects and wheezing was the first symptom in rest. About 60% had severely impaired PFTs, and these patients responded to glucocorticosteroid better than the COPD-only patients. In the asthmaonlygroup, most complained of wheezing as the first symptom and had better PFTs. However, sputum eosinophilic granulocyte was as high as ( 13. 5 ±3. 1) % . They responded to glucocorticosteroid effectively.Conclusions COPD and asthma were both obstructive airway inflammatory diseases, but pulmonary function and responses to glucocorticosteroid therapy were different. It is necessary to understand the severity and mechanism of airway function impairment in order to improve the proper diagnosis and treatment of asthmaand COPD in elderly.