OBJECTIVE: The relationship between paranoia symptoms and underlying prefrontal cortex mechanisms among healthy subjects was analyzed using near-infrared spectroscopy. METHODS: Seventy-eight healthy subjects were assessed for paranoia symptoms using the Japanese version of the Paranoia Checklist. Changes in hemoglobin concentrations were assessed using 2-channel near-infrared spectroscopy on the surface of the prefrontal cortex while subjects performed a verbal fluency test. RESULTS: Changes in the concentration of oxygenated hemoglobin in the prefrontal cortex during a verbal fluency test did not correlate with the Japanese version of the Paranoia Checklist. CONCLUSION: Our findings show that the symptoms of paranoia do not negatively affect the prefrontal cortex function among healthy subjects.