The aim of this study was to perform a pioneering investigation into the incidence of pneumatization in human skulls. A total of 93 human skulls (≥20 years of age, 69 males, 24 females) were included in the study. The skulls were scanned in a fixed position using cone beam computed tomography (CBCT). The pneumatized space parameters within the nasal septum-width, length, and height-were measured. Two types of finding were identified: (a) Pneumatization, named "sinus septi nasi" (SSN), and (b) "spongy bone" (SB). The results showed SSN in 32 of the 93 skulls (34.4%). The SSN formations were from 0.5 to 4.2 mm wide, 3.5 to 18.8 mm long, and 3.8 to 17.7 mm high. Tumefactions filled with SB were found in 61 of the 93 skulls (65.59%). These were not suitable for precise measurements since the outer borders were not strictly and well defined on CT scans (perhaps because of the preparation process). In conclusion, the perpendicular plate of the ethmoidal bone is not always compact bone; in 34.4% of cases, it shows a degree of pneumatization. In contrast, an enlarged formation filled with SB is present in 65.59% of cases. The possible sources of pneumatization of this little-investigated region are discussed: sphenoid sinus, frontal sinus, and vomeronasal organ.