By the classical diagnostic methods for the paranasal sinusitis, such as anterior rhinoscopy and plain X-ray, it is difficult to decide between conservative treatment and surgical intervention. In case of selection of the surgical methods, anterior rhinoscopy and plain X-ray don't give much information to the surgeon. And then, by such classical diagnostic method, we could not get much information about the degree of blockage of the ostiomeatal unit and the reversibility of the mucosal change in the maxillary sinus. In order to find out the dergee of blockage of the ostiomeatal unit and reversibility of the mucosal change in the maxillary sinus, we performed nasal endoscopy and sinoscopy through the canine fossa under the local anesthesia on the twenty-two patients with paranasal sinus problems. By that findings, we tried to choose the suitable surgical method for each patient and it was possible to reduce unneeded Caldwell-Luc operation. We would like to present the procedures and the endoscopic findings of five typical cases.