Neuroblastoma is sometimes associated with abnormal constitutional karyotype, but the XYY karyotype has not been described in neuroblastoma except Japanese one case. Y chromosome may play a role in the pathogenesis of neuroblastoma as well as leukemia. Therefore we report a case of esthesioneuroblastoma with a 47, XYY karyotype. A 6-year-old male was admitted to the hospital with complaints of bilateral nasal obstruction and cervical lymphadenitis without hepatosplenomegaly. CBC showed White blood cell count 11,000/uL, hemoglobin 12.5 g/dL, platelets 363,000/uL. Urinalysis revealed normal levels of vanillyl mandelic acid (7.56 mcg/mg creatinin), homovanillic acid (14.3 mcg/mg creatinin), but elevated levels of serum neuron-specific enolase (50.9 ng/mL). Bone marrow aspiration did not disclose blastic cells. Biopsy of the right nasal polyp was performed and the patient was diagnosed as having olfactory neuroblastoma. N-myc gene amplification did not perform due to severe bleeding tendency of nasal mucosa. Cytogenetic analysis was performed by bone marrow preparation after a 48-hour culture without stimulation, and demonstrated a 47,XYY karyotype in somatic cells. After all, the patient diagnosed esthesioneuroblastoma, intermediate risk although several factors as the following; advanced age, suspicious cervical lymph node metastasis (INSS, Stage 3). Therapeutic assessment was that the main therapy was chemotherapy performed 12th cycles, except the autologous stem cell transplantation. An XYY male may present with a wide variety of physical and behavioral clinical features. In treatment period, he appeared behavioral violence and temper tantrum, so we refered psycologic consultation and started methylpenidate for treatment of behavior disorder.