The study of the structure of the maxillary sinus floor is of great clinical importance in surgical interventions. The presence or absence of premolars and molars affects the change in the ratio of compact and spongy bone tissue. Objective. To study the structure of the maxillary sinus in patients of different ages with varying degrees of edentia according to CBCT data. Material and methods. 248 upper jaws were studied using CBCT: a total of 496 left and right maxillary sinuses. Cases of the presence of premolars and molars, absence of a premolar and/or molar, and complete absence of premolars and molars were identified. The results of the study show that the presence of premolars and molars affects the ratio of the volume of spongy and compact bone. With the loss of chewing teeth, the volume of trabecular bone tissue decreases, the volume of compact bone increases. Discussion. The presence or absence of premolars and molars of the upper jaw affects the volume of compact and spongy tissue in the area of the floor of the maxillary sinus, which is of great clinical importance when planning surgical interventions in this area.