Radiation-induced leukoencephalopathy presents clinically as a cognitive disorder chronologically associated with radiotherapy. The characteristic findings are: acute reversible edema, demyelination and vascular necrosis associated with thrombosis. The diagnostic test of choice is magnetic resonance imaging (MRI) and the treatment is with corticosteroids. We present a case of a patient with brain metastases who developed a post-radiotherapy leukoencephalopathy.