Carbon dioxide intoxication is a rare condition and only few case reports are found in the literature. There were six patients who suffered from carbon dioxide intoxication in our hospital about two years ago. Two of them are more severe with conscious change and brain MRI studies of the two patients were performed. Reviewing the literature, no any report has mentioned about the encephalopathy associated with carbon dioxide intoxication. We want to review the brain lesions on the diffusion weighted images and the laboratory data of the patients for further diagnostic help.