Anatomical variants of the sinonasal cavities are common. About 15 major variants are described (nasal septal deviation is present in up to 62% of the population). Because the may lead to complications at the time of endovascular procedures or endoscopic sinonasal surgery (vascular, nervous, or osseous injury), there detection has medicolegal implications. Knowledge of anatomical variants by radiologists and ENT surgeons is thus required. We will describe these variants, their imaging features, frequency, implications and associated risk of potential complication.