Two cases of acute carbon monoxide poisoning are presented in this paper. Sequential magnetic resonance (MR) images of the brain showed abnormal lesions in the bilateral globus pallidus and/or in the subcortical white matter. The MR images disclosed that the severity of the white matter lesions correlated with the prognosis in acute carbon monoxide poisoning. However, they did not always correspond to the neurological condition in the acute and subacute stages.