A case of psychotic disorder with a right temporal lesion was reported. The patient, a 19 year old male, who underwent a brain surgery to remove the trigeminal Schwannoma, occupying from the right cerebellopontine angle to the right middle cranial fossa. One year postoperatively, he presented with a psychotic disorder, including auditory hallucinations, delusions of persecution and reference, thought hearing, thought insertion and passive experiences. T1-weighted images on magnetic resonance imaging (MRI) demonstrated a low intensity signal area in the right temporal cortex and white matter. T2-weighted images demonstrated a high intensity signal within the same region. Single photon emission computed tomograghy (SPECT) demonstrated a severe low perfusion corresponding to the region in which the MRI demonstrated the abnormalities. The clinical and neuroimaging studies of this case suggest that psychotic disorder may occur in association with a right temporal lesion and MRI and SPECT are useful to evaluate an organic basis for the psychotic disorder.