〔Abstract〕 Objective To investigate the changes of cerebral blood flow(CBF) in patients with type 2 diabetes mellitus(T2 DM) and its correlation with cognitive function and olfactory impairment. Methods Cognitive function assessment and smell identification test were performed on 83 patients with T2 DM and 62 healthy controls(HC). Three-dimensional pseudo-continuous arterial spin labeling(3 D-pcASL) head images were collected from the two groups. CBF values of the cerebral cortex were compared between the patients and HC after the postprocessing. Correlations between the CBF values and cognitive function assessment and between the CBF values and smell identification test scores were analyzed as well. Results Compared to the HC, Chinese smell identification test(CSIT), montreal cognitive assessment(MoCA), digit span test(DST), verbal fluency test(VFT) scores were lower in T2 DM patients(P<0.05).The CBF of the bilateral middle frontal gyrus in T2 DM patients was higher than that in HC group(P<0.001). The CBF of the bilateral gyrus rectus and olfactory cortex in T2 DM patients was lower than that in HC group(P<0.001). Conclusion The cognitive and olfactory function of patients with T2 DM decreased. Patients with T2 DM have abnormal perfusion in the bilateral middle frontal gyrus, gyrus rectus and olfactory cortex, revealing that CBF changes in these brain regions may be one of the causes for cognitive impairment and olfactory dysfunction in T2 DM.