Introduction: We aimed to classify different degrees of cerebrovascular insufficiency (CVI) in patients with moyamoya disease (MMD) by measuring cerebral blood flow (CBF) and distinguishing arterial transit artifacts (ATAs) on arterial spin labeling (ASL) magnetic resonance imaging (MRI). Methods: The study included 121 images of patients with MMD who underwent ASL-MRI before and after surgical treatment (242 hemispheres). On ASL-CBF maps, regions of interest (ROIs) were manually drawn in each hemisphere in seven zones. Quantitative and qualitative patterns of arterial transit artifacts (ATA) were studied. Analysis of variance (ANOVA) was used for group comparisons. Results: Distinguished patterns were divided into four statistically significant degrees on the basis of CBF values and the presence of ATA: degree 0 with normal CBF values and without ATAs (n = 59) (CBF 60.37–68.64 mL/100gxmin); degree 1 with moderate decreased CBF and with ATAs (n = 97) (CBF 55.82–62.16); degree 2 with significantly decreased CBF and with ATAs (n = 64) (CBF 25.64–28.96); and degree 3 with very low CBF and without ATAs (n = 22) (CBF 15.58–19.97). All groups exhibited significant differences between the value of CBF in all cortical territories (p < 0.01). Distinguished patterns had high correlations between Suzuki stage, the severity of ischemic disease, and neurologic deficit. Conclusion: The revealed ASL-MRI patterns correspond to the degree of CVI, the stage of the disease, and the clinical symptoms and can be used for assessment in the patients with moyamoya disease.