In MR cerebral vasoreactivity (CVR) experiments, responses to the gas stimuli are expected to be with no major time lag. However, it has been shown that different brain regions could respond with different timing during a vasoreactivity. The presence of potential latencies could lead to a misinterpretation of the resulting CVR maps. We attempt to correct CVR maps for physiological latency differences, and propose an alternative way to display both corrected CVR and CVR latency. The data from a Moya Moya patient highlight that even without a strong perfusion alteration, the vasoreactivity is strongly delayed or even completely disrupted.