A 69-year-old woman was admitted to our hospital due to an interval form of carbon monoxide (CO) poisoning one month after acute CO poisoning. On admission, she had disorientation, memory disturbance, apathy, masked face, muscle rigidity, bradykinesia and parkisonian gait. An MRI (FLAIR image) revealed high signal intensity lesions in the bilateral globus pallidus and the white matter of the frontal lobe. Hyperbaric oxygen (HBO) therapy at 2 atmospheres for 60 min was given every day, in addition to citicoline, levodopa/DCI and selegiline hydrochloride. Cognitive disturbance and parkinsonism gradually decreased, and abnormal signals in the bilateral globus pallidus and the cerebral white matter were attenuated after the treatment. Neuropsychiatric abnormalities except for a slight gait disturbance disappeared one and a half month after starting the treatment. In addition to HBO therapy, administration of citicoline, lovodopa and selegiline may be useful in the case of the interval form of CO poisoning.