Background: The purpose of the present study is to investigate the frequency and amount of extension of the maxillary sinus to the anterior region and to evaluate the vertical distance between the maxillary sinus floor and canine apices.Methods: Cone beam computed tomographic images of 300 individuals (154 males and 146 females) over 20 years (with mean age of 35.12 ± 8.40 years) were evaluated. The subjects were categorized into three age groups (20-30, 30-40 and 40-50 years). When maxillary sinus extended to the canine area, the vertical distance between them were recorded and their relationship were classified into three types: I (> 2 mm distance), II (2 mm < distance or in-contact) and III (interlock). Results: 413 out of 600 maxillary sinuses (68.8%) were extended into the canine area or beyond. Among them, 15 maxillary sinuses pneumatized into the incisor area (2.5%). The prevalence of the maxillary sinuses extended to the anterior region of the jaw was not significantly different between genders, but it was significantly less frequent in older age group and more frequent in the left side. The mean amount of anterior extension of maxillary sinus (mm) was significantly lower in older age group. Type I was the most frequent vertical relationship between the maxillary sinuses and canine apices with no significant difference in gender, side and age groups.Conclusions: Most of the maxillary sinuses extended to the canine area. Maxillary sinus extended into incisor area with the frequency of 2.5% . The amount of extension of the maxillary sinus to the anterior region and its vertical distance with canine apices decreased in older age group.