Objectives : The purpose of this study is to evaluate the computed tomographic (CT) images of the paranasal sinusitis(PNS). Materials and Methods : The author examined the extent and recurring patterns of the paranasal sinusitis and some important anatomic landmarks. The author analyzed PNS images retrospectively in 500 patients who visited Chonbuk National University Hospital between January 1996 and December 1997. Results : The most frequently affected sinus was maxillary sinus (82.9％), followed by anterior ethmoid sinus(67.9％), posterior ethmoid sinus(48.9％), frontal sinus(42.0％) and sphenoid sinus(41.4％). The characteristic features of CT images of the sinusitis were sinus opacification(22.4％), mucoperiosteal thickening(34.3％), and polyposis(2.0％). Sinonasal inflammatory diseases were categorized into 5 patterns according to Babber s classification. They were 1) infundibular(13.0％), 2) ostiomeatal unit(67.4％), 3) sphenoethmoidal recess (13.0％), 4) sinonasal polyposis (9.6％) and 5) unclassifiable patterns(18.0％). The incidences of contact between sinus and optic nerve were as follows ; the incidences of contact with posterior ethmoid sinus, sphenoid sinus. both posterior sinuses were 11.4％. 66.8％, 6.3％. respectively. The incidences of contact between sphenoid sinus and maxillary nerve, vidian nerve, internal carotid artery were 74.5％. 79.2％. 45.1％. respectively. The incidences of pneumatization of the posterior ethmoid sinus were as follows ; normal 70.6％ and overriding type 29.4％. The incidences of sphenoid sinus pneumatization were as follows; normal 56.9％ , rudimentary 12.5％, pterygoid recess 22.7％, anterior clinoid recess 2.7％, and both pterygoid and anterior clinoid recess type 5.2％. Conclusions : The inflammatory sinonasal diseases were classified into five patterns using the CT of PNS, which was proven to be an excellent imaging modality providing detailed information about mucosal abnormality, pathologic patterns, and the proximity of the important structures to the posterior paranasal sinuses. This result will aid in the interpretation of CT of PNS functionally and systemically.