Objective To study the concentration distribution of acetone in fasting exhaled breath in diabetic patients and healthy subjects,to explore the effect of individual indexes on the concentration of acetone in fasting exhaled breath,and to study the role of individual indexes of fasting exhaled breath acetone in diabetes screening.Methods The acetone concentration measurements of fasting exhaled breath were performed on 265 healthy subjects,39 patients with type 1 diabetes (T1D),and 300 patients with type 2 diabetes (T2D) using real-time online respiratory acetone analyzer based on cavity ring-down spectroscopy (CRDS).SPSS 19.0 software was used to eliminate outliers,and relevant statistical analysis was carried out with the corresponding gender,age,height,body mass,body mass index (BMI) and blood glucose concentration (BGL).The receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value of fasting breath acetone concentration for diabetes diagnosing.Results The mean fasting breath acetone concentration in T1D patients was (2.24±1.43)×10-6 was significantly higher than (1.43±0.55)×10-6 in healthy subjects and (1.41±0.73)×10-6 in T2D patients,and the differences were statistically significant (all P＜0.05).The average fasting breath acetone concentration in male diabetic patients was higher than that in female patients.The mean fasting breath acetone concentration was positively correlated with age (R=0.31,P＜0.01) in healthy subjects,was positively correlated with BMI (R=0.33,P＜0.05) in T1D patients,and was positively correlated with height (R=0.18,P＜0.01) in T2D patients.The area under the ROC curve for the diagnosis of T1D by fasting breath acetone concentration was 0.853 with a sensitivity of 71.9％ and specificity of 87.4％ (P＜0.01),and for the diagnosis of T2D was 0.528 with a sensitivity of 54.1％ and specificity of 55.0％ (P＞0.05).Conclusions The detection of fasting breath acetone concentration is meaningful for T1D diagnosing,but has a low accuracy for T2D diagnosing (no statistically significant).