Since the introduction of functional ednoscopic sinus surgery, the importance of the ostiomeatal unit(OMU) has been known. And it is believed that any anatomical variation that can cause obstruction of OMU may be the cause of sinusitis. From this point of view, the septal deviation can be one of the causes of sinusitis. Also it is generally agreed that the convex side of the septum is more prone to be affected. On our series, however, opposing side predilection has been observed as compared to previous reports. We have selected twenty three cases of unilateral sinusitis with septal deviation through coronal CT scan : sinusitis on the concave widened side of the nasal cavity is 20 ; only 3 cases on the convex narrow side. We propose a possible mechanism through which this phenomenon can be developed : widened nasal cavity will increase inspiratory air flow which may impair mucociliary clearing function of the mucosa about the infundibulum and the natural ostium, eventually obstructs whole ostiomeatal complex.