Ostiomeatal unit(OMU) CT is widely accepted for endoscopic sinus surgery. Various anatomic findings that is seen in the OMU CT are essential in preoperative evaluation. Patterns of sinusitis are relatively good indicator for prognosis. We reviewed the 80 cases, 160 sides of OMU CT for analysis of anatomic structures and patterns of sinusitis, and report as follows : 1) The main type of olfactory fossa was type II (80%). 2) The most frequent site of insertion of uncinate process was lamina papyracea(56.9%). 3) The incidence of anatomic variation was as follows : Haller's cell(5%), concha bullosa(13.8%), paradoxically bent middle turbinate(3.8%), dehiscent lamina papyracea(2.5%), and double middle turbinate(1.3%). 4) The number of septum of frontal and sphenoid sinuses was 1 in 60% and 47.5%, respectively. 5) Type of pneumatization of sphenoid sinus was distributed as follows : sellar(68.7%), presellar(25%), conchal(6.3%). 6) The incidence of patterns of sinusitis was as follows : sinonasal polyposis(44.2%), OMU(33.3%), infundibular(11.6%), sporadic(8%), sphenoethmoidal recess(2.9%).