Background: Congenital nasal pyriform aperture stenosis (CNPAS) leading to respiratory insufficiency in infants has been well documented. Nevertheless, the nasal pyriform aperture stenosis (NPAS) entity in adulthood has not been discussed at all. The normative data of the width of the pyriform aperture, which has not been revealed before, is necessary for evaluation of the adult subjects with nasal bony inlet stenosis. The aim of this study was to define the normative data about the pyriform aperture width measured in 80 adult subjects with paranasal sinus symptoms without nasal obstruction. and, additionally, to report the surgical results of two representative cases with NPAS.