Background The chronic obstructive pulmonary disease assessment test (CAT) is an easy to use health-related quality of life questionnaire,the modified Medical Research Council (mMRC) dyspnea scale is a classic dyspnea scale which is widely used,while the correlation between them is still not clear.This study investigated the use of the Chinese translation of CAT in chronic obstructive pulmonary disease patients and its correlation with the mMRC dyspnea scale.Methods The multicenter cross-sectional study was conducted in 329 hospitals throughout China from March 1 to April 30,2010.Chronic obstructive pulmonary disease patients completed both the assessment test and the dyspnea scale during a single study visit.Results Six thousand,four hundred and thirty-seven patients were evaluated; 74.9％ were male and the mean age was (64.9±10.0) years.Median test scores in dyspnea grades 0 to 4 were 14,16,22,26 and 32,respectively; these differences were statistically significant.The CAT score was moderately correlated with mMRC dyspnea grade (r=0.579,P ＜0.001).There was no significant difference in mean CAT score between males and females,and patients of high and low socioeconomic status.Pdmary analysis suggested that CAT scores were higher in older patients (＞65 years) than in younger patients (≤65 years) and increased with duration of formal education,but these findings were repudiated by further analysis of subgroups according to mMRC dyspnea grade.Conclusions There was no obvious confounding factor influencing use of the CAT in Chinese patients.CAT scores were moderately correlated with the mMRC dyspnea scale.