Esthesioneuroblastoma is a rare neuroectodermic tumor of the olfactory tract. An 18F-FDG PET/CT was performed in a 75-year-old woman with cervical lymphadenopathy. It demonstrated focal intense uptake (SUVmax, 72 g/mL) in an occult sphenoclival tumor. Anatomopathological examination of the lymphadenopathy and the primary tumor biopsy revealed well-differentiated esthesioneuroblastoma. Explaining the paradox between tumor differentiation and PET findings, immunohistochemistry showed low Ki-67 but overexpression of GLUT-1 suggesting an activation of hypoxia pathways. Unlike many solid tumors, FDG avidity is not correlated with histological grade in esthesioneuroblastoma. The tumor biology may clarify the discrepancy between metabolic activity and cellular mitotic processes.