The aim of the present study was to compare the anatomy of the cavernous sinus via an endoscopic transnasal route with the anatomy of the same region explored by the transcranial route. The purpose was to identify and correlate the corresponding anatomic landmarks both through the endoscopic transnasal transsphenoidal and the microscopic transcranial views. Five fresh injected heads (10 specimens) were dissected by the endoscopic transnasal and microsurgical transcranial approaches. A comparison of different microsurgical corridors of the cavernous sinus with the corresponding endoscopic transnasal ones was performed. Through the endoscopic transnasal approach, it is possible to explore only some of the parasellar and middle cranial fossa subregions. Because of the complex multilevel architecture of the cavernous sinus, there is not always a correspondence between the surgical corridors bounded through the transcranial route and those exposed through the endoscopic transnasal approach. Nevertheless, some surgical corridors specific to the endoscopic transnasal route are evident: a C-shaped corridor is identifiable medial to the "intracavernous" internal carotid artery, whereas a wider triangular area is delineable lateral to the internal carotid artery; inside the latter, three more surgical corridors (a superior triangular space, a superior quadrangular space, and an inferior quadrangular space) can be described. Different surgical corridors can be defined during the endoscopic transnasal approach to the anteroinferior portion of the cavernous sinus, as already established for the transcranial route as well. Knowledge of these could be useful in decreasing morbidity and mortality during surgery in this region, these approaches being reserved to experienced transsphenoidal surgeons only.