Objective: The aim of this study was to determine blood flow volume (BFV) in the normal state and its features in patients with acute posterior circulation ischemic strokes (PCIS) and vertebrobasilar insufficiency (VBI) using color duplex sonography (DS).Methods: The study included DS data from 96 patients with verified PCIS (66 men and 30 women, aged 64±13 years) and 29 adults with VBI (17 men and 12 women, aged 66±11 years). The control group consisted of 65 healthy male volunteers of different ages.Results: In asymptomatic healthy volunteers, there was a significant decrease in BFV in the internal carotid artery (ICA) with age (502 ml/min in young people, 465 ml/min in the older subgroup) with rS = −0.24 ( p = 0.05), and the aggregated BFV in the vertebral arteries (VAs) turned out to be almost constant (141–143 ml/min). In patients with VBI, the aggregated BFV in the VAs (144 ml/min) did not differ from that in healthy volunteers, but the BFV values in the ICAs were significantly lower (325 ml/min). In patients with PCIS, the aggregated BFV in the ICAs was also significantly lower (399 ml/min) than in the control group but did not significantly differ from that in patients with VBI. In patients with PCIS, there was a significant decrease in the aggregated BFV in the VAs (105 ml/min), which distinguished this group from other examined patients.Conclusions: A significant decrease the BFV in the VA was observed only in patients with PCIS and was associated with the presence of steno-occlusive diseases (SOD) more often in the left VA. Patients with VBI had the most pronounced decrease in BFV in the ICA.