The prerequisite for a nasal endoscopic surgeon to safely and effectively perform endoscopic sinus surgery (ESS) is familiarity with the anatomy of the paranasal sinuses. However, there are significant variations in sinus anatomy, so endoscopic sinus surgeons need to carefully review the images before ESS. The pneumatization variation of the ethmoid sinus determines the difficulty of opening the frontal sinus, sphenoid sinus, and maxillary sinus during ESS, so preoperative identification of pneumatization variation of the ethmoid sinus is particularly important. The posterior ethmoidal cell (PE) also has significant variability and can extend toward areas such as the orbital region, infraorbital region, and sphenoid body. Based on previous anatomical studies and recent literature of the PE, this paper summarizes the types of pneumatization extension in the PE, including the origin of the cell, the location of the cell, adjacent structures around the cell, and their significance for ESS, with a view to enhancing the understanding of these variations among rhinologists.