Objective To analyze the differences in computed tomography(CT)myocardial perfusion parameters between type 2 diabetes mellitus(T2DM)patients and nondiabetic patients diagnosed with non-obstructive coronary artery disease(CAD),using a one-stop cardiac CT scanning protocol that combines coronary CT angiography(CCTA)with dynamic CT myocardial perfusion imaging(CT-MPI).In addition,we investigated the effect of T2DM on coronary microcirculatory ischemia.Methods After balancing the baseline levels with propensity score matching,92 T2DM patients(the T2DM group)and 92 nondiabetic patients(the nondiabetic group)with non-obstructive CAD were enrolled eventually.The clinical characteristics and the CCTA and CT-MPI results of the two groups were compared.A directed acyclic graph was used to analyze the causal relationships between the variables and to identify key confounding factors.A multivariable regression model was established to evaluate the independent effect of T2DM on the occurrence of coronary microcirculatory ischemia after adjusting for confounding factors.Results There were no statistically significant differences between the T2DM group and the nondiabetic group in terms of age,sex,hypertension,hyperlipidemia,smoking history,body mass index,chest symptoms,calcium score,CAD-reporting and data system(CAD-RADS)score,and radiation dose.In the T2DM group,the mean values of myocardial blood flow(MBF)were significantly reduced both globally and in all myocardial segments(basal,mid,and apical segments)compared to those of the nondiabetic group(P＜0.05).Furthermore,the incidence of coronary microcirculatory ischemia in the T2DM group was significantly higher than that in the nondiabetic group(21.7％[20/92]vs.5.4％[5/92],P=0.01).Multivariable logistic regression analysis showed that T2DM was an important independent risk factor for coronary microcirculatory ischemia(odds ratio=5.095,95％confidence interval:1.753-14.805).Conclusion According to our assessment with a one-stop cardiac CT scanning protocol combining CCTA and dynamic CT-MPI,patients with non-obstructive CAD and T2DM have reduced global MBF,which makes them more prone to coronary microcirculatory ischemia.Furthermore,T2DM is independently associated with coronary microcirculatory ischemia.