Eighteen cases of cystic lesions of paranasal sinuses which were treated at Inje College, Busan Baik Hospital for 8 years from June 1979 to May 1987 were clinically observed. The results were as follows; 1) Cystic lesions of the paranasal sinuses were 18 cases(0.36%) of 4867 patients who admitted for past 8 years. Of 18 cases, postoperative maxillary cyst showed 10 cases(55.6%) and mucocele showed 4 cases(22.2%) and pyocele showed 2 cases(11.1%) and radicular cyst showed 2 cases(11.1%). 2) The age distribution was in 31-40 years group(6 cases, 33.3%), in 41-50 years group(5 cases, 27.7%), in 11-20 years group(3 cases, 16.7%), in 21-30 years group(2 cases, 11.1%), in 51-60 years group(1 case, 5.6%), in 61-70 years group(1 cases, 5.6%). Postoperative maxillary cyst was predominant in 31-40 years group(5 cases, 50%). 3) The sex distribution showed 9 cases(50.0%) of males and 9 cases(50.0%) of females. Cases of mucocele and pyocele were predominant in males. 4) Mucocele and pyocele were located on the frontal sinus showing 3 cases(50%), on the frontoethmoid sinus showing 2 cases(33.3%) and on the maxillary sinus showing 1 case(11.6%). Postoperative maxillary cyst was located on left side showing 8 cases(80%). 5) There were all 5 cases having frontal swelling and ocular Sx., 3 cases(60%) having frontal pain on the mucoceles of frontal sinus and frontoethmoid sinus. There were 11 cases(84.6% having cheek swelling and 7 cases(53.8%) having cheek pain on the cystic lesions of maxillary sinus. 6) Time lag from onset of clinical symptoms to admission ranged from one month to 2 years and duration for 1 year was 5 cases(100%) in cystic lesions of frontal sinus and 10 cases(83.3%) in cystic lesions of maxillary sinus. 7) There were no specific relationship between the age at the previous sinus surgery and duration of Sx. in postoperative maxillary cyst. 8) Contents of cystic lesions were frequently mucoid type in 5 cases(50%) and mucopurulent type was next in 4 cases(40%).