The radiological anatomy of the ethmoid was poorly understood until the arrival of tomographic methods, especially computed tomography. Mouret, Professor at the Faculty of Medicine of Montpellier, devoted himself to the study of this anatomical region and proposed a systematic description of the ethmoid. The usual plain X-ray view of the sinuses present certain defects because of bony superimposition. The OM + 20 degrees view of the base of the skull proposed by G. Guillen appears to be the most precise view for the study of the anatomy and physiology of the region, as it coincides with the axis of drainage of the ethmoidal air cells.