Postoperative cheek cyst develops from the scar tissue of the post-operative maxillary cavity and reveals the symptoms of the cheek swelling, the cheek pain and discomfort, toothache, etc. over 10 years after the initial Caldwell-Luc's operation. The Caldwell-Luc's operation is one of the most common operation procedures of the chronic maxillary sinusitis in Korea. The authors analyzed 47 cases of the postoperative cheek cyst who were admitted to the Dept. of Otolaryngology, S.N.U.H. from 1963 to 1976. There were 35 males and 10 females with a sex ratio of 3 : 1. Age distribution was from 29 to 63 years, the highest age group was 5th decade 20 cases (42.5%) and the next 4th decade with 12 cases (25.5%). The postoperative time lag was 9 to 44 years and 18 cases (38.3%) had visited the hospital 21~25 years after the initial Caldwell-Luc's operation. The chief complaints were cheek swelling (32 cases), cheek pain and tenderness (29 cases), toothache (12 cases), headache, paresthesia, lacrimation, nasal discharge, nasal obstruction, exophthalmos and diplopia, oro-antral fistula. The operative findings revealed the partial defect of the sinus bony wall (40.1%), remnants of sinus mucosa (18.5%), complete obstruction of the previous nasoantral window with fibrous tissues, the discharge containing the various sized cyst. The content of the cyst was mucoid, purulent and mucopurulent.