Maxillary sinus hypoplasia (MSH) is an uncommonly, encountered condition by otolaryngologists. Pie computerized tomography (CT) scans provide valuable data about the anatomic details of the paranasal sinuses. MSH may, be misdiagnosed as an infection or a neoplasm of the maxillary, sinuses. Variations of the other paranasal structures, especially the uncinate process associated with MSH were defined. MSH shows three distinct hypoplasia patterns. Type I MSH characteristics are mild hypoplasia of the maxillary sinus, normal uncinate process and a well-developed infundibular passage. Significant hypoplasia of the maxillary, sinus, hypoplastic or absent uncinate process and absent or pathologic infundibular passage are seen in Type II MSH. Type III MSH is characterized by the absence of an uncinate process and cleft-like maxillary, sinus hypoplasia. In this study a series of 18 patients with MSH were presented. Twelve cases of unilateral and 6 cases of bilateral maxillary, antrum hypoplasia were evaluated and 13 MSH hype 1, 7 MSH type II and 4 MSH type III were detected. Three ethmomaxillary sinuses, an overpneumatized posterior ethmoid cell into the orbit and the maxillary sinus were determined. Our series showed that the uncinate process anomalies related to MSH malY lead to inadvertent orbital complications and therefore should be kept in mind.