BACKGROUND Among patients with ICA stenosis, there are some cases with elevated, undisrupted, and diminished cerebral blood flow (CBF). The aim of this study was to assess the influence of ICA stenosis treatment on postoperative CBF changes in relation to preoperative CBF values. MATERIAL AND METHODS We qualified 58 patients ≥65 years old (28 males, 30 females, mean age 71.02±6.34 years) for surgical intervention due to symptomatic ≥70% ICA stenosis. In all patients, a flow volume in all extracranial arteries (internal carotid [ICA], external carotid [ECA], and vertebral arteries [VA]) was measured preoperatively and 2-3 days following the surgery. The CBF values were compared with the ones established for a healthy population of the same age. RESULTS Preoperatively, there were 3 subgroups of patients, comparing to healthy population: with elevated CBF - "significant compensation," with undisrupted CBF - "mild compensation," and with diminished CBF - "no compensation." Postoperatively, a significant CBF increase was observed in patients with preoperative "no" and "mild compensation" - 277.18±154.26 ml/min (P=0.0000001) and 221.56±98.8 ml/min (P=0.0000001). In a "significant compensation" group, there was no flow increase observed (CBF change of 2.57±58.5 ml/min, P=0.954) - a redistribution of flow was observed. CONCLUSIONS In patients with lower preoperative CBF values, surgical treatment caused a significant increase in global cerebral inflow, which was more prominent in patients with the lowest preoperative CBF. In patients with high preoperative CBF, surgical treatment resulted in a flow redistribution, but did not cause a CBF increase. Volumetric flow assessment in DUS can predict hemodynamic benefit from surgery in terms of CBF increase.