['Changes in apparent diffusion coefficient (ADC) values often reflect tissue injury. Use of ADC as a surrogate marker to assess clinical phases has not been systemically applied in patients with carbon monoxide (CO) intoxication.', 'Fifty-nine magnetic resonance imaging scans and cognitive evaluations were performed in 47 patients with CO intoxication and compared with 22 sex- and age-matched controls. The patients were further classified into three groups based on the clinical phases, namely, acute (within 2 weeks), delayed neuropsychiatric (2 weeks to 6 months), and chronic (>1 year) groups. The ADC values were measured in 16 regions of interests (ROIs) and correlated with cognitive test scores.', 'Among the 59 evaluations, 15 were in the acute, 26 in the delayed neuropsychiatric, and 18 in the chronic groups. Among the ROIs, significant elevations of ADC values were found in the corpus callosum and globus pallidus in all three CO phases compared with the controls, and the ADC values were highest in the chronic phases. In contrast, the ADC values in peripheral gray matter and white matter were highest in the delayed neuropsychiatric group. Both globus pallidus and corpus callosum ADC values correlated with multiple cognitive test scores.'] Does diffusion-weighted imaging improve prediction in cognitive outcome and clinical phases in patients with carbon monoxide intoxication?