The almost simultaneous introduction of nasal endoscopy and CT imaging led to better understanding of normal and pathologic function of the paranasal sinuses. Diagnosis and treatment of many paranasal sinus diseases improved considerably. Endoscopy and CT are not concurrential; they are complementary, but they have specific strengths and weaknesses, as well as specific indications and considerations. Staging systems for chronic sinusitis are currently used based on CT findings and response to medical therapy. Functional endoscopic sinus surgery (FESS) has become the standard procedure for most surgical cases of chronic sinusitis. Indications for FESS have enlarged beyond chronic sinus problems and even beyond the borders of the sinuses. Functional endoscopic sinus surgery aims to gain maximal result (restoring normal function) with minimal trauma and morbidity.