Objective: Piriform aperture, paranasal sinuses, and the cranium dimensions were compared with each other and we investigated the alterations depending on the age and gender in these structures. Before the endoscopic sinus surgery, anatomic variations in sinusoidal region and the occurring differences should be considered. The detection of these variations plays important roles in the prevention of complications which may happen in surgery or in obtaining a successful surgical result. Materials and Methods: Piriform aperture maximum width, frontal sinuses, sphenoidal sinuses,maxillary sinuses, and craniumwidths and height length was measured from the regions that we were determined. Three hundred ninety three cases computed tomography images were compared. The individuals without any head trauma, pathology, and surgical history in sinusoidal region were analyzed retrospectively. The detected measurements were studied among the paranasal sinuses, piriform aperture, and calvaria dimensions. Results: It was observed that the dimensions of paranasal sinuses were decreased and the dimension of piriform aperture was increased depending on age. In all individuals, a relationship in positive direction in a manner that piriform aperture width increases as the size of the cranium width increases. Morphologic alterations take place in the dimensions of paranasal sinuses as a result of bone deformations occurring in the bone structure depending age and gender in adult individuals.