Purpose: The aim of this study was to evaluate the prevalence of clinically relevant anatomical variations of the ethmoid sinuses and their potential association with ethmoid and maxillary sinus pathologies on cone-beam computed tomography (CBCT) scans. Additionally, potential associations with different sides and demographic factors, including age and sex, were evaluated. Materials and Methods: In total, 273 CBCT scans with complete ethmoid and maxillary sinuses were analyzed to determine the prevalence of Agger nasi cell, supraorbital ethmoid cell, Haller cell, Onodi cell, and ethmomaxillary sinus. In addition, the health or pathology of the ethmoid and maxillary sinuses was also recorded to assess correlations with the aforementioned variations. Results: The prevalence of Agger nasi cell was found to be the highest (95.6%) in this study, followed by Onodi cell (60.4%), Haller cell (29.3%), and supraorbital ethmoid cell (19.4%). Ethmomaxillary sinus was the least common finding (16.5%). Males and persons above 61 years of age had a significantly higher frequency of supraorbital ethmoid cell and Onodi cell, respectively. However, no significant relationships were noted between anatomical variations of the ethmoid sinus and pathologies of the ethmoid or maxillary sinus. Conclusion There was a high prevalence of ethmoid sinus variations in this Southern Chinese population. The prevalence of Agger nasi cell and Onodi cell was higher than that of other anatomical variations of the ethmoid sinuses. Anatomical variations of the ethmoid sinuses were not associated with ethmoid or maxillary sinus pathologies in this patient cohort.