Objective:To investigate the predictive value of regional leptomeningeal collateral (rLMC) score on CT angiography (CTA) for the outcome after endovascular therapy in patients with late window anterior circulation stroke.Methods:Patients with acute anterior circulation large vessel occlusive stroke received endovascular treatment 6 to 24 h after onset in the Department of Neurology, the First Affiliated Hospital of Soochow University from January 2018 to July 2021 were enrolled retrospectively. At 3 months after onset, the outcome was evaluated according to the modified Rankin Scale. A score of ≤ 2 was defined as good outcome, and a score of >2 was defined as poor outcome. The clinical data, non-enhanced CT and CTA parameters of the patients were collected. Multivariate logistic analysis was used to determine the independent influencing factors of poor outcomes after endovascular treatment. Results:A total of 74 patients with acute anterior circulation large vessel occlusive stroke treated with endovascular treatment in the late window were enrolled. Their age was 64.41±12.98 years, 43 were males (58.1%). The baseline National Institutes of Health Stroke Scale (NIHSS) score was 13.18±5.22, and the median time from onset to puncture was 527.5 min. Fifty-three patients (71.6%) chose direct thrombectomy and 21 (28.4%) chose intravenous thrombolysis and bridging thrombectomy. Thirty-six patients (48.6%) had a good outcome and 38 (51.4%) had a poor outcome, including 4 (5.4%) died. Univariate analysis showed that there were significant differences in age, atrial fibrillation, fasting blood glucose, NIHSS score, Alberta Stroke Program Early CT Score (ASPECTS), rLMC score and clot burden score between the good outcome group and the poor outcome group (all P<0.05). Multivariate logistic regression analysis showed that higher ASPECTS (odds ratio 0.352, 95% confidence interval 0.157-0.791; P=0.012) and rLMC score (odds ratio 0.550, 95% confidence interval 0.329-0.919; P=0.022) were the independent predictors of good outcomes after endovascular therapy. Conclusion:ASPECTS and rLMC scores were the independent predictors of clinical outcomes after endovascular therapy in patients with late window anterior circulation large vessel occlusive stroke. It had certain guiding value for the decision-making of endovascular treatment in such patients.