Recent clinical trials have shown that patients with large ischemic cores have better outcomes with endovascular thrombectomy (EVT) compared with standard medical treatment (SMT) alone.We aim to assess whether the relationship between EVT and improvements in clinical outcomes varies depending on the location of the occlusive sites.This study is a subgroup analysis conducted within a prospective, nationwide, multi-center registry. The cohort included patients with acute large vessel occlusion in the anterior circulation and an Alberta Stroke Program Early Computed Tomography Score of 0 to 5 within 24 hours from last known well. We utilized the adjusted common odds ratio for a shift toward better outcome on the modified Rankin Scale after EVT compared with SMT alone as the primary outcome. Safety outcomes included symptomatic intracranial hemorrhage (sICH).A total of 745 patients with large ischemic cores were included: 272(36.5%) with internal carotid artery occlusion, 392(52.6%) with M1 segment of the middle cerebral artery occlusion, and 81(11.0%) with M2 segment of the middle cerebral artery occlusion. The adjusted common odds ratios were as follows: 1.98 (95% CI, 1.01-3.89) for ICA occlusions, 2.09 (95% CI, 1.35-3.23) for M1 occlusions, and 1.13 (95% CI, 0.43-2.94) for M2 occlusions. There was no significant treatment-by-occlusion site interaction observed (P=0.69). However, the incidence of sICH was significantly greater in all groups receiving EVT than in those receiving SMT alone. Additionally, we observed that the secondary outcomes and subgroup analyses were generally consistent with the main outcomes.In this study, we found that patients with internal carotid artery and M1 occlusion demonstrated a better outcome with EVT, while the benefit for patients with M2 occlusion remains uncertain.Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc.