To quantify differences in physiological cerebral blood flow parameters (mean transit time, cerebral blood volume, cerebral blood flow, area affected) between acute ischemic stroke patients with presence of any kind of intra-cranial vessel abnormalities, and those with neck vessel abnormalities. Prospective registry of all patients with stroke presenting to the ED of an academic tertiary care center, undergoing a CT perfusion scan. CT angiogram neck and head of patients were reviewed to understand which of these patients had any abnormalities in their neck vasculature (carotids, vertebrals and basilar arteries) and intra-cranial vasculature. CT perfusion scans of patients were also reviewed, to analyze, mean transit time (MTT), cerebral blood volume (CBV), cerebral blood flow (CBF) and size of the ischemic area of interest. Ischemic areas were defined as any area that had significant prolongation in the mean transit time of blood flow. Penumbra was identified from this area as the region with relative preservation of cerebral blood volume. Individual values of MTT, CBV and CBF were also noted in both these areas for each patient. Of the total 74 patients with acute ischemic stroke, 24% had abnormalities detected in the intra-cranial vasculature, 20% had neck vessel abnormalities, and 29% had abnormalities in both systems. Patients with only abnormalities in the intra-cranial vasculature had significantly higher areas of blood flow compromise (median 61 sq cm, IQR 6.9 to 91.5 sq cm) when compared to patients with neck vessel abnormalities (median 6.6 sq cm, IQR 0 to 47.2 sq cm; p=0.023). Similarly penumbric area was also higher for patients with intra-cranial vessel abnormalities (median 44.8 sq cm, IQR 5.4 to 86.2 sq cm) when compared to patients with neck vasculature defects (median 4.3 sq cm, IQR 0 to 46.5 sq cm; p=0.037). As expected patients with affection of both these systems had even higher ischemic area (median 106.4 sq cm) and penumbric area (median 61.4 sq cm). There were, however, no differences noted between these two groups of patients, with regards to the MTT (p=0.646), CBF (p= 0.975) and CBV (p=0.232) of the demarcated ischemic area. On further analysis, a trend was seen. The MTT was the longest (median 8.9s) , the CBV was the least (median 2.3) and the CBF was the minimum (median 17.9) in the ischemic area for patients with affection of both systems, when comparing all 3 groups together. There are no differences with regards to mean transit times, cerebral blood volume and cerebral blood flow rate, in ischemic brain areas between acute stroke patients with intra-cranial vessel abnormalities and neck vasculature defects. Patients with intra-cranial vessel abnormalities, though, do have a larger area at risk for infarction when compared to patients with cervical vasculature abnormalities. Patients with abnormalities in both systems had the worst cerebral blood flow parameters amongst stroke patients.