INTRODUCTION: Many neurotrauma patients suffer from higher brain dysfunction even when focal brain damage is not detected with MRI. We performed functional imaging with positron emission tomography (PET) to clarify the relationship between the functional deficit and symptoms of such patients. METHODS: Patients who complain of higher brain dysfunction without apparent morphological cortical damage were recruited. Thirteen patients underwent PET study to image glucose metabolism by (18)F-FDG, and central benzodiazepine receptor (cBZD-R) by (11)C-flumazenil, together with measurement of cognition. RESULTS: Diffuse axonal injury (DAI) patients have a significant decrease in glucose metabolism and cBZD-R distribution in the cingulated cortex than normal controls. Score of cognition test was variable among patients. The degree of decreased glucose metabolism and cBZD-R in the dominant hemisphere corresponded well to the severity of cognitive disturbance. Patients with a milder type of diffuse brain injury (i.e., cerebral concussion) also showed abnormal glucose metabolism and cBZD-R distribution when they suffered from cognitive deficit. CONCLUSION: PET molecular imaging was useful for depicting the cortical dysfunction of neurotrauma patients even when morphological change was not apparent. This method may be promising in clarifying the pathophysiology of higher brain dysfunction of patients with neurotrauma, but without morphological abnormality.