Objective To explore the predictive value of posterior circulation-Alberta Stroke Program early computed tomography score(pc-ASPECTS) based on cerebral computed tomography perfusion(CTP) for prognosis of patients with acute ischemic stroke caused by vertebral and basilar artery occlusion(VBAO-AIS).Methods The data of 56 patients with VBAO-AIS who received endovascular treatment in the Neurovascular Center, Changhai Hospital, Naval Medical University(Second Military Medical University) from Jan. 2019 to Dec. 2020 were retrospectively analyzed. All patients underwent emergency multimodal computed tomography(CT) examination, and the pc-ASPECTSs based on non-contrast computed tomography(NCCT), CTP and RAPID-CTP were obtained. The modified Rankin scale(mRS) score 3 months after treatment was used to evaluate prognosis(mRS score ≤ 3 indicated good prognosis). Receiver operating characteristic(ROC) curve and multivariate logistic regression analysis were used to evaluate the prognostic value of pc-ASPECTS based on NCCT and each parameter of CTP and RAPID-CTP.Results Among the 56 patients, 29 had good prognosis and 27 had poor prognosis. The pc-ASPECTSs based on NCCT and each parameter of CTP and RAPID-CTP were significantly higher in the good prognosis group than those in the poor prognosis group(all P<0.05). The sensitivities of CTP cerebral blood volume(CBV) pc-ASPECTS and RAPID-CBV pc-ASPECTS in predicting prognosis were 89.7% and 79.3%, the specificities were 74.1% and 81.5%, and the area under curve values were 0.861(95% confidence interval[CI]0.760-0.963) and 0.861(95% CI 0.764-0.958), respectively. Binary multivariate logistic regression analysis showed that NCCT pc-ASPECTS ≥ 8, CTP CBV pc-ASPECTS ≥ 7, CTP mean transit time(MTT) pc-ASPECTS ≥ 5, RAPID-CBV pc-ASPECTS ≥ 8, and RAPID-cerebral blood flow(CBF) pc-ASPECTS ≥ 7 were independent factors in predicting good prognosis of VBAO-AIS patients 3 months after endovascular treatment(all P<0.05).Conclusion pc-ASPECTS based on each parameter of CTP is a useful prognostic marker of VBAO-AIS patients. In particular, CBV pc-ASPECTS has a high predictive value for the prognosis of VBAO-AIS patients 3 months after endovascular treatment.