The ciliary area of the maxillary sinus mucosa and coronal sinus computed tomographic (CT) scans were studied in 36 maxillary sinuses of 28 patients with chronic sinusitis. Tissue specimens allowed ciliary surfaces to be observed under scanning electron microscopy, allowing surfaces to be expressed in terms of ciliary area (CA) as the percentage of mucosal surface occupied by cilia. The opacity produced by mucosal swelling and secretion in the maxillary sinus on CT was assessed by two methods: Min's and modified van der Veken's methods. Both techniques indicated an inverse correlation between opacity of the maxillary sinus and CA. Our findings suggest that the opacity of maxillary sinus on CT could be a significant parameter for predicting the surface conditions of ciliated maxillary mucosa prior to sinus surgery.