Most authors feel that the maxillary sinus and dento-alveolar arch do not develop normally in case of choanal atresia. This as explained by respiratory deficiency on the atretic side. A series of 11 cases of unilateral choanal atresia, either untreated or treated after the period of maximum growth, have been studied by clinical examination, serial X-rays and cephalometric tracings in order to compare atretic and normal sides. No significant difference has been found, neither for size nor shape of the maxillary sinus. These observations are therefore in contradiction to earlier reported findings and require further study.