Surface and tissue transitional concentration of 3% FOM aerosol for treatment of paranasal sinusitis was examined in 18 patients (21 sides) who underwent the Caldwell-Luc operation. In this operation, patients have a bony window on the sinus; we therefore investigated the difference of compliance of the maxillary sinus between when we closed the bony window with subcutaneous tissue and when we did it with a silicone sheet before the FOM nebulization. No significance was found in the mean concentration of FOM either at the maxillary sinus surface or in the tissue with or without the use of the silicone sheet. We also examined the concentration using a jet-type nebulizer and an ultra-sonic type nebulizer. Using the ultrasonic-type nebulizer resulted in a higher transitional concentration at two sites of the maxillary sinus surface than when using the jet-type nebulizer. The results suggest that the ultrasonic-type nebulizer is more effective in the treatment of paranasal sinusitis than the jet-type, and that there was no change of maxillary sinus compliance with or without a bony window.