Pulmonary arteriovenous malformations (PAVM) are mostly associated with hereditary hemorrhagic telangiectasia (HHT). We report two pediatric patients diagnosed with HHT on the basis of PAVM who died because of cerebral and spinal AVM rupture. Two 4-year-old boys were diagnosed with PAVM due to hypoxia. Case 1: This patient underwent transcatheter embolization for PAVM four times, but the efficacy was limited. He suffered a complication in the form of cerebral AVM and was treated conservatively. We diagnosed him with HHT because of recurrent epistaxis, telangiectasia of the skin, and AVM. Genetic tests revealed a mutation in the gene for endoglin. At the age of 7 years and 5 months, he died of cerebral AVM rupture. Case 2: Transcatheter embolization could not be performed because of multiple, diffuse PAVM. The patient was complicated by spinal AVM and treated conservatively. We suspected HHT because of telangiectasia of the skin and AVM. At the age of 5 years and 6 months, he died of spinal AVM rupture. HHT is vascular dysplasia that is expressed in multiple organs, and sepsis is the main cause of death. We tend to treat PAVM. But because cerebral and spinal AVM are common as the cause of death, we should check for other forms too, such as cerebral and gastrointestinal AVM, and continue long-term follow-up with concomitant consultation. However, untreatable or unexpected manifestations may occur in these cases, making HHT difficult to treat.