Until the 1990s, radical sinus surgery was considered a standard procedure for maxillary sinus diseases, but it is no longer favored due to the high morbidity. Today, functional endoscopic sinus surgery (FESS) is considered the gold standard in sinus surgery. Modifications of surgical approaches also allow access to regions of the maxillary sinus that were previously difficult to reach. Depending on anatomy and pathology, different methods for widening the maxillary ostium can be selected. In type I sinusotomy, the natural ostium is widened dorsally by a maximum of 1 cm. Sinusotomy type II involves widening the natural ostium up to a maximum diameter of 2 cm. In sinusotomy type III, the natural ostium is widened dorsally to the posterior wall of the maxillary sinus and caudally to the base of the inferior turbinate. Beside the prelacrimal approach, more invasive approaches are the medial maxillectomy, in which the dorsal part of the inferior turbinate and the adjacent medial wall of the maxillary sinus is resected, as well as its modifications "mega antrostomy" and "extended maxillary antrostomy." Correct selection of the size of the maxillary sinus window is prerequisite for successful treatment and long-term postoperative success. Isolated purulent maxillary sinusitis can usually be treated by a type I sinusotomy. Sinusotomy type II addresses nasal polyps with involvement of the mucosa of the ostium, recurrent stenosis after previous surgery, chronic maxillary sinusitis due to cystic fibrosis, and purulent maxillary sinusitis with involvement of other adjacent sinuses. Sinusotomy type III is required for choanal polyps with attachment to the floor of the maxillary sinus, for extensive polyposis and fungal sinusitis, and for inverted papilloma. Particularly for (recurrent) disease and extensive interventions in the maxillary sinus, medial maxillectomy or a modification thereof may be required.