Introduction : Neurofibroma is a benign nerve sheath tumor in the peripheral nervous system.. Neurofibroma can occur in a sporadic fasion, or in association with a genetic neurocutaneous disorder such as neurofibromatosis type 1 (NF1). Neurofibromas that are associated with NF1 are association with NF1 gene expression from the long arm of chromosome 17 (17q). Loss of NF1 gene expression leads to increased levels of activated RAS.1,2. RAS-mediated cell growth promotes unregulated growth. Neurofibromas and optic gliomas, as well as pathognomonic findings of pigmented nodules of the iris (Lisch nodules) and pigmented skin lesions (café au lait spots) was associated with loss of NF1. We are to report a 17-year-old patient of vagus nerve neurofibroma in neurofibromatosis type 1. Case Mediastinal widening was observed incidentally on x-ray in local and was hospitalized for further evaluation. In past history, he had right hemiplegia due to moyamoya disease in 1 years old. There is a history of diagnosis of neurofibromatosis including father and grandfather. he was asymptomatic and was admitted to our hospital for evaluation mediastinal widening in local X-ray. Laboratory findings showed Hb 15.8g/dL; hematocrit (Hct) 44.5%; WBC count 6,900 μL; platelets count 176,000 μL; AST(GOT) 31 IU/L; ALT(GPT) 37 IU/L CRP 0.50 mg/L.. he was performed Chest CT and MRI, and T1 low & T2 high signal intensity lobulating longitudinal mass-like lesion showing target appearance along the right vagus nerve & left vagus or phrenic nerve was observed, which indicated neurogenic tumor such as neurofibromatosis rather than Schwannoma. Gold-standard treatment of symptomatic benign vagus nerve mass is an attempt at gross total resection with minimal loss of nerve function. But he has no symptoms. Considering the side effect of surgery such as Horner, vocal cord palsy, tongue fasciculation, We decided to observe the change in size by observation of progress rather than surgical treatment. Conclusion: A 17-year-old child was asymptomatic and mediastinal widening was observed incidentally on x-ray in local. There is a history of diagnosis of neurofibromatosis including father and grandfather and moyamoya disease in 1 years old. We are to report a case of accidentally observed vagus nerve neruofibromas in the 17-year-old diagnosed as neurofibromatosis.