Various kinds of second malignant neoplasms after sucessful treatment for childhood acute leukemia have been reported. The authors describe an unusual case of an olfactory neuroblastoma in a patient previously treated for childhood acute leukemia including autologous bone marrow transplantation. The prophylactic cranial irradiation and the total body irradiation during autologous bone marrow transplantation may have induced the development of their patient's olfactory neuroblastoma. Although a second primary olfactory olfactory neuroblastoma is rare is rare, it should be added to the list of second malignant neoplasms in the sinonasal region.