A 20-year-old male patient was found unconscious and delivered to our emergency department by ambulance for suspected carbon monoxide poisoning. When he arrived to the emergency department, there was no neurologic finding. Initial brain computed tomography failed to show any damage. His laboratory results were within reference range, except carboxyhemoglobin being 40%. Dual-energy computed tomography (DECT; as far as we know, first in the literature) revealed perfusion defect as it showed hypodense areas on the right temporal lobe. He was transferred in the emergency intensive care unit. In addition to normobaric oxygen treatment, 2 sessions on the first day and 1 session on the second and thirds days of hyperbaric oxygen treatment were performed. Control DECT was taken on the fourth day of hospitalization after hyperbaric oxygen treatment was completed. Control DECT revealed a decrease in iodine uptake and relative recovery in perfusion on the same region. After relief of his complaints and with total recovery in neurologic examination, the patient was discharged to follow-up with recommendations on his fourth day of admission. We conclude that brain DECT may be useful for both the diagnosis and the effectivity of treatment in patients with carbon monoxide intoxication who had neurologic symptoms.