Introduction. Application of an implant in the posterior maxilla sometimes is challenging especially when there is present maxillary sinus pathology. In certain clinical situations it can still be performed simultaneously with sinus clearance. Objective. To evaluate the treatment features of implantation in patients with bone insufficiency in the posterior site of the maxilla in the presence of maxillary sinus pathology. Material and methods. Patient C.S., M/26 years old presented to the dental clinic "Omni Dent" with complaints about missing teeth in the posterior sector of the upper jaw. During clinical and paraclinical examination was established diagnosis: partial bilateral partial dentition in the maxilla, Kennedy class 2 with missing teeth 15, 16, 26, 27, caused by dental caries complications, associated with a cystic formation on the sinus floor on the right side. Results. A typical lateral sinus lift operation was performed, with exception of completing it with the removal of the mucosal cyst through the created window, aspiration of cyst contents and membrane, followed by subsequent stages: creation of neoalveoli, protection of the Schneiderian membrane defect with A-PRF, augmentation with synthetic biomaterial "KP3-LM", implantation and suturing. Clinical and radiological evaluation at a distance of 1 year demonstrated the effectiveness of the approach method in virtue of morphofunctional rehabilitation and the absence of complications. Conclusions. The method of implant treatment in the presence of maxillary sinus mucosal cyst can be performed simultaneously with sinus clearance and is one of the preferred methods for reducing overall treatment time.