BACKGROUND Although chronic paranasal sinusitis has been recognized and diagnosed more frequently in recent years, it is still one of the most frequently overlooked disease and a significant source of morbidity and economic loss. Therefore, a further detailed analysis of its clinical pictures and computed tomographic (CT) presentations is necessary for better understanding. METHODS We collected 230 cases in recent two years and studied their CT manifestations. RESULTS The pathological changes of sinusitis on CT were classified into four groups: mucosal thickening, mucosal thickening combined with fluid level, fluid level only, and total sinus opacification, in increasing frequency. Maxillary sinus was the most commonly involved sinus. Focal high density areas were noted in 17 sinuses. Ten of them were operated and revealed only thick mucous without evidence of calcification or fungal infection. There was no correlation between the disease duration and the number of sinuses involved. CONCLUSIONS CT is the image modality of choice in evaluating patients with chronic paranasal sinusitis.