Objectives: Mucous retention cysts and pseudoantral cysts are mainly located within the floor of the maxillary sinus. Most of these maxillary cysts are asymptomatic and often only require observation. However, the presence of these benign maxillary cysts may create problems when maxillary sinus all types of implants are needed. Various treatment methods have been introduced. The selected treatment option depends on the type, size, and location of the cyst and its symptoms. Patients and Methods: The case reports of four patients with maxillary cysts were reviewed retrospectively. These patients received a sinus lift between January 2016 and October 2021 at the Wonkwang University Dental Hospital. Results: To reduce unnecessary operations and the duration of treatment, a conservative treatment method is required. A sinus lift in the presence of maxillary cyst will not typically cause sinus problems if the lifted sinus membrane does not interfere with ventilation of the maxillary sinus. Conclusion When proper treatment is provided, sinus perforation during a sinus lift performed in the presence of maxillary cyst and contamination of bone graft materials by cystic fluid does not necessarily result in adverse outcomes.