Objective-To diagnose hyperacute(<3hrs duration of symptoms) ischemic infarct and differentiating penumbra from core infarct by using CT perfusion technique. Material and method- The study was conducted on 40 patients of acute stroke using 128 slice MDCT scanner first NCCT were done to rule out hemmoragic infarction and other pathologies followed by 40 milliliters of a nonionic contrast agent at a rate of 4 mL/sec. 5 seconds after initiation of the injection, a cine (continuous) scan was initiated for duration of 45 seconds. CT perfusion data was analyzed at an imaging workstation (Syngo Acquisition workstation; Siemens healthcare Systems) equipped with commercially available software (Stroke MTT; Siemens Healthcare Systems). Results: out of 40 patients, 8 patients presented within 3 hours of symptoms and the sensitivity of NCCT in detecting Ischemic infarct within 3 hours is 26 % whereas that of CTP was 87.4%. rCBF of tissue at risk was 0.64 ± 0.12 and that of core infarct was 0.35 ± 0.05. the rCBV of tissue at risk was 0.80 ± 0.16 and rCBV of core infarct was 0.29 ± 0.11 Conclusion:- Considering all the parameters studied, CT Perfusion was found to be more sensitive than NCCT in diagnosing acute ischemic stroke and was better in differentiating salvageable penumbra from non salvageable core infarct.