ObjectiveTo investigate and compare the clinical characteristics of chronic obstructive pulmonary disease (COPD) and asthma-COPD overlap syndrome (ACOS). MethodsA case-control study was conducted in 139 patients with COPD who admitted between March 2013 and September 2013. The patients were divided into a COPD-only group and an ACOS group. Clinical data were collected and compared between two groups. ResultsOf all 139 patients, 93 patients were diagnosed with COPD only (66.9%) and 46 patients were diagnosed with ACOS (33.1%). Compared with the COPD-only group, the ACOS group had a lower ratio of exposure to cigarette smoking (80.4% vs. 93.5%), but high possibility of a history of asthma (89.1% vs. 4.3%), allergies (60.9% vs. 9.6%) and airway hyperreactivity (80.4% vs. 6.5%) (P < 0.05). In clinical symptoms, the ACOS group had a higher ratio of breathless as the first complaint of symptom (26.1% vs. 8.6%) and dry and moist rales in lung by auscultation (67.4% vs. 31.2%) (P < 0.05). In laboratory examination, the ACOS group had increased levels of peripheral blood eosinophils and IgE than those of the COPD-only group (21.7% vs. 5.4%, 18.3% vs. 4.3%, P < 0.05). In treatment, the ACOS group was more likely to use systemic glucocorticoid (58.7% vs. 24.7%) and be treated with higher dosage of glucocorticoid (80 mg, P < 0.05). ConclusionsACOS and COPD-only are two subtypes of COPD. Compared with COPD-only patients, ACOS patients might be more likely to be breathless and have dry and moist rales in clinical symptoms, more likely to have increased levels of peripheral blood eosinophils and IgE in blood test, and more inclined to receive systemic glucocorticoid treatment.