A 45-year-old woman was admitted to our department because of intracerebral hemorrhage. Neurological examination showed upward gaze palsy, right hemihypesthesia including face and nuchal rigidity. CT scan demonstrated a high density spot in the left quadrigeminal plate. Postcontrast CT scan demonstrated an abnormal vessel in the left midbrain. We suspected the presence of an arterio-venous malformation (AVM) and angiography was performed. Left vertebral angiography demonstrated early filling as far as the basal vein of Rosenthal with the contrast medium. However, no nidus suggesting AVM was observed. The right middle cerebral artery was fed via an anastomotic vessel (anomalous posterior communicating artery) from basilar bifurcation. Right carotid angiography demonstrated only the right external carotid artery indicating the absence of the right internal carotid artery. The bone target image of thin slice CT scan of the cranial base also disclosed the absence of the right carotid canal. 123I-IMP SPECT demonstrated no hypoperfusion area in the right cerebral hemisphere. The usefulness of the thin slice CT scan in the cranial base was discussed.