Objective: To investigate the correlations between carotid plaque characteristics and cerebral blood flow (CBF) in patients with unilateral moderate to severe carotid stenosis using high-resolution magnetic resonance imaging (HR-MRI) and 3D pseudo-continuous arterial spin labeling (3D pcASL). Methods: A total of 43 patients with unilateral moderate to severe carotid stenosis were recruited. The degree of carotid stenosis, maximum wall thickness (Max WT) and normalized wall index (NWI) were measured using HR-MRI. The plaque characteristics were analyzed. Presence or absence of plaque components including intraplaque hemorrhage (IPH), lipid-rich necrotic nucleus (LRNC), calcification and ulcer were identified, and the grades of calcification and LRNC were recorded. CBF values within the region of interest representing the bilateral middle cerebral artery distribution were acquired using 3D pcASL. Paired sample t test was used to compare the differences of CBF values between the index side and the contralateral side. Spearman correlation analysis was conducted to evaluate the correlations of CBF values with the degree of carotid stenosis, Max WT and NWI. The differences of CBF values between the patients with or without IPH and ulcer were compared using Mann-Whitney U test. Different levels of calcification and LRNC were compared by Kruskal-Wallis test, respectively. Results: The ave-rage degree of carotid stenosis at the index side was 77.30%±11.79%. The mean CBF value of the index side was (46.77±11.65) mL/(100 g·min), and that of the contralateral side was (49.92±9.95) mL/(100 g·min), and the difference was statistically significant (t=-2.474, P=0.017). The mean Max WT and NWI of the carotid plaques at the index side was (6.40±1.87) mm and 62.91%±8.87%, respectively. There were no significant correlations of CBF values with the degrees of stenosis, Max WT and NMI (P>0.05). Plaque composition analysis showed that the CBF values of the index side were different when there was calcification or not and the degrees of calcification were different (P=0.030), but there were no differences between the CBF values on the index sides with or without IPH, ulcer and LRNC. Conclusion: In patients with unilateral moderate to severe carotid stenosis, calcification might affect CBF perfusion. When there is no calcification, the plaque components need attention.