In this article the authors describe a rare case of olfactory neuroblastoma in a 55-year-old woman surgically treated because of nasal polyposis. Three years earlier she had been operated for nasal polyposis on the same side in another ENT department. Unfortunately these lesions may had not been evaluated histologically. One of the surgically removed polyps was atypical. In histopathological examination it was confirmed to be olfactory neuroblastoma. CT scan revealed abnormal thickness of the mucosa in the upper part of the nose and ethmoidal sinuses on the right side. The tumor was classified as stage B in Kadish classification of olfactory neuroblastoma. The histopathologic diagnosis and CT scan made after the surgery resulted in necessity of further oncological treatment. The olfactory neuroblastoma is rare, difficult to diagnose, malignant, slowly growing tumor arising from the olfactory epithelium in the upper nasal cavity. The treatment includes surgery, radiotherapy and chemotherapy. Another objective of this paper is to point out that histopathological examination is crucial in each surgically removed tissue.