The state of the mucoperiostasis of the maxillary sinus is one of the important factors that affect the effectiveness of dental implantation, especially in case of need for augmentation of the maxillary bone. Chronic rhinosinusitis with nasal polyps, chronic rhinosinusitis with fungal bodies, and sinus cysts are among the most common pathological processes in the maxillary sinus that are encountered when performing subantral augmentation. In addition, a separate category of patients is made up of those with a history of sinus surgery in their anamnesis. The condition of sinus mucoperiosteum can be estimated based on results of processus uncinatus research, because it has a similar histological structure, directly contacts with all maxillary sinus excretion and, as usual, gets removed while endoscopic sinusotomy. The purpose of the work was to study the histological features of mucoperiostasis and adjacent bone in the ostiomeatal complex in discrete diseases of paranasal sinuses: chronic rhinosinusitis with nasal polyps, maxillary sinus cysts, fungal balls and postoperative scar changes in the ostium. Materials and methods. Histological features of processus uncinatus fragments removed during endoscopic interventions in 45 patients were investigated: with sinus cysts – 12 patients (group 1), chronic rhinosinusitis with nasal polyps – 13 patients (group 2), sinus fungal body – 13 patients (group 3) and postoperative scarring changes in the ostiomeatal complex – 7 patients. The condition of the epithelial layer of the mucoperiosteum, the structure of its own plate, the periosteal layer and the bone to be treated were evaluated. Results and discussion. In 91.67 ± 0.08% of patients with maxillary sinus cysts, there were no changes in the mucoperiostasis and the bone of processus uncinatus. Most patients in groups 2 and 3 showed mucoperiostal edema with a predominant reaction of the mucosal layer and lamina propria. Fibrous changes of the processus uncinatus were most often detected after the intervention was performed at 71.43 ± 0.13% and in chronic rhinosinusitis with nasal polyps – 53.85 ± 0.14%. This confirms the significance of the mucoperiostasis injury factor with the underlying bone for the development of gross adhesive changes between the periosteum and bone tissue. Osteitis of the processus uncinatus was detected in 38.46 ± 0.13% of patients in group 2, 15.38 ± 0.1% in group 3, and 28.57 ± 0.17% in group 4. Conclusion. Signs of periostitis and processus uncinatus osteitis were most often detected in patients with neutrophilic mucoperiosteum infiltration in chronic rhinosinusitis with nasal polyps and in fungal balls sinus. History of surgery with periosteal and bone trauma promotes scarring and results in a tight connection between bone and periosteum, which can be regarded as a risk factor in relation to the rupture of the later in its peeling off during sinus lifting procedure. Therefore, when performing surgery on the maxillary sinus, in order to maintain conditions for possible dental implantation, excessive trauma of the periosteal layer of mucoperiosteum should be avoided