PURPOSE: Acute posterior circulation stroke (PCS) is characterized by often non-specific clinical signs, with neuroimaging playing a pivotal role in assessment in the emergency setting. The aim of this study was to investigate the effectiveness of CT Perfusion (CTP) maps in detecting acute PCS and to identify clinical factors associated with perfusion abnormalities. METHODS: We retrospectively analyzed clinical and radiological data of consecutive patients with acute PCS admitted to our Stroke Unit that underwent CTP. Follow-up NECT or MRI was performed to confirm the diagnosis of PCS. The effectiveness of CTP to identify PCS was evaluated as the ratio of the CTP in which perfusion abnormalities, compatible with an ischemic event, were present in at least one CTP map among MTT, CBF, TTP, and CBV. Multivariate logistic regression analysis was conducted to identify clinical factors associated with perfusion abnormalities. RESULTS: CTP showed alterations in 69 of 107 PCS (64.5%) included in final analysis and MTT proved to be the most sensitive. Multivariate analysis showed that atrial fibrillation (OR = 8.571, CI 95% 2.224-33.037, p = 0.002), dyslipidemia (OR = 0.285, CI 95% 0.100-0.814, p = 0.019), visual field deficits (OR = 3.372, CI 95% 1.020-11.150, p = 0.046), and higher neurological deficit (NIHSS >
5) (OR = 4.054, CI 95% 1.147-14.331, p = 0.030) were significantly associated with perfusion abnormalities on CTP. CONCLUSION: CT perfusion can be a valuable resource for detecting acute PCS showing a moderately high positivity rate, higher than that of NECT alone or CTA. These findings contribute to the growing body of evidence supporting the use of perfusion imaging in acute posterior circulation stroke.