Hereditary hemorrhagic telangiectasia (HHT) is easily overlooked in patients with central nervous system (CNS) lesions. Our clinical experience of three patients with CNS lesions associated with HHT stresses the importance of considering HHT. A 23-year-old male presented with consciousness disturbance and right hemiparesis. Emergency cerebral digital subtraction angiography revealed occlusion of the left middle cerebral artery and the left anterior cerebral artery. Pulmonary arteriography showed three pulmonary arteriovenous malformations (AVMs). A 62-year-old male presented with consciousness disturbance and sensory aphasia. Magnetic resonance imaging revealed a ring-enhanced lesion in the left temporal lobe which was removed by left frontotemporal craniotomy. The diagnosis was brain abscess. Chest computed tomography (CT) revealed two pulmonary AVMs. A 32-year-old female presented with progressive mild weakness in her left hand. Initial CT showed subcortical hemorrhage in the right frontal lobe. Cerebral angiography revealed no vascular malformations, but chest CT disclosed five pulmonary AVMs. All three patients had a family history of HHT. The possibility of HHT is important to consider in patients with cerebrovascular disease (CVD) or brain abscess to prevent complications, not only in the patients but also their blood relatives. Therefore, the medical and family history of patients with CVD or brain abscess should be investigated and HHT should be considered during the physical examination.