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Near-occlusion (NO) with and without full collapse seems to cause low blood flow in symptomatic carotid stenosis. If the stroke mechanism is hypoperfusion in NO, the stump pressure should be low. The aim was to compare and describe stump pressure and blood flow in conventional ≥ 50% stenosis, NO without full collapse, and NO with full collapse. In this prospective single-center study, consecutive patients with symptomatic ≥ 50% carotid stenosis (NASCET grading), undergoing carotid endarterectomy (CEA) were recruited. NO was diagnosed by three blinded observers who reviewed computed tomography angiographies (CTA). Intraoperative measurements of ICA flow before and after CEA and stump pressure were recorded. One hundred and eighty-one patients were included; 116 (64%) had conventional ≥ 50% stenosis, and 66 (36%) had NO. Before CEA, the median ICA flow was significantly lower in NO (90 ml/min) compared to conventional ≥ 50% stenosis (170 mL/min, p < 0.001). In contrast, no difference was observed after CEA (NO 170 mL/min, conventional ≥ 50% stenosis 180 mL/min, p = 0.48). The ICA flow change was significantly higher in NO compared to conventional stenosis (p < 0.001). There was a significant correlation between the distal ICA diameter on CTA and the ICA flow before CEA (r = 0.579, p < 0.001). There were no differences in stump pressure between NO and conventional ≥ 50% stenoses (median 53 (range 41–66) mmHg and median 54 (range 40–67) mmHg, respectively, p = 0.93), nor any correlation between the stump pressure and the distal ICA diameter (r = 0.063, p = 0.41). NO causes low ICA flow, and to our knowledge, this is the first time this causal link between ICA flow and NO is clearly established. Since patients with NO did not have low stump pressure, the mechanism of stroke in NO does not seem to be hypoperfusion.