The postoperative maxillary cyst develops as a delayed complication many years after surgical intervention in the maxillary sinus. Clinically, the patient usually complains the swelling or pain of the cheek and the mucogingival fold of maxilla. Histologically, the cyst appears to be derived from the epithelial lining of the maxillary sinus which apparently has been trapped in the wound during closuse of the incision and subsequently begins to proliferate. We have treated 5 cases of postoperative maxillary cyst which were confirmed pathologically during recent 1 year. The results are as follows; 1. In case 1, we have found the independent 4 cystic cavity which were very rare. 2. In most cases, the chief complains were midfacial or buccal swelling. 3. The above all cysts were developed after Caldwell-Luc`s operation about 10-33 years ago. 4. distribution was in 2nd-5th decade. 5. In all cases, the patients complained the associated tooth symptoms. During the cyst treatment, we have proper tooth treatment together, the results of which were favorable.