In studying 2,500 head C-T scan of Chinese, the incidence of cava septi pellucid et Vergae is very low as compared to the reported non-Chinese incidence from many authors. Only 1% of the incidence was found from 2,500 Chinese aged from 6 months to 60 years old. The incidence of cavum septum pellucidum was found to be 0.32 %, and the incidence of coexistence of both cava septi pellucidi et Vergae was 0.68%. There was no cavum Vergae alone in 2,500 Chinese. It might be racial characteristics. Pseudoventricular formation resembling to the cava septi pwllucidi et Vergae was noted in many conditions; cortical atrophy, hydrocephalus and senile cerebral degeneration. As compared to the other reports in literature, C-T scan is better than any other methods in the diagnosis because of its simple, timesaving and accuracy.