Computed tomography (CT) scanning of the paranasal sinuses provides valuable information in assessing extent of disease and fine detailed anatomy prior to endoscopic sinus surgery. Awareness of the different anatomic variants of the bony sinonasal anatomy will help the rhinologic surgeon's orientation during the procedure. We conducted a study to look at the incidence of the anatomic variation within the lateral wall of the nose and sinuses and to determine if there is any ethnic difference in these variants between a cohort of 100 Caucasian patients undergoing endoscopic sinus surgery in London and 100 Chinese patients treated in Hong Kong. We compared the two groups with chi-square test and the significant areas are those with p value of less than 0.05. The results show a higher incidence of pneumatisation of the middle turbinate (concha bullosa) and paradoxical bending of the middle turbinate in the Caucasian population. The infraorbital and suprabullar cell development was greater in the Caucasian population though the incidence of sphenoethmoidal cells was much greater in the Chinese population. When asymmetry of the anterior ethmoidal roof was considered, the left was consistently the highest in both groups, though there was no difference in the depth of the cribiform niche between right and left or between Caucasian and Chinese. The incidence of bent uncinate process and of complete absence of a sinus was higher in the Chinese population. There was no difference in the presence of pneumatisation of the agger nasi, of the uncinate process, or of the anterior clinoid process. There was no difference in the presence of septation adjoining the carotid in the lateral wall of sphenoid or in the exposure of the optic nerve within sphenoid or posterior ethmoid sinuses. Although there is no evidence that variants of the sinonasal anatomy seen on CT Scan have a causative effect in the disease process; a knowledge of their presence is paramount in minimising the potential for surgical complications.