Objective: In this clinical retrospective study, Mle aimed to evaluate giant hydatid lung cyst cases as a different clinical entity that recorded in last 10 years in our clinic. Methods: Between February 1990 and May 2000, a total of 305 hydatid lung cyst cases from patients that had been operated were reviewed, and 67 (21.9%) cysts with more than 10 cm in diameters of them were regarded as a giant hydatid lung cyst. Further investigations were made with respect to different factors. Results: Thirty-six (54%) cases were male and 31 (46%) were female. The ages ranged between 5 and 54 (mean 21.6) years. The most common symptoms recorded were; cough (68%), thoracic pain (55%) and dyspnea (52%). Cyst sizes were ranged between 10 and 22 cm (mean 13.4) in diameters. Forty-two (62%) of them were in the right, 22 (33%) were in the left hemithorax, and three (5%) were located bilaterally. Cystotomy or cystectomy and capitonnage was the most frequent applied operation procedure (71%). Resection was performed in nine (13%)cases. Thirteen(19%) cases had air leakage more than 10 days in which five (7%) of them empyema occurred postoperatively. One case died due to respiratory failure in fourth postoperative day. The postoperative hospital stay ranged between 6 and 43 (mean 10.5) days. No recurrence was recorded in 1-5 years of a follow-up period. Conclusions: Giant hydatid lung cysts must be regarded as a different clinical entity because of their early occurrence, having more serious symptoms, with frequent operative complications, and they need prolonged care with higher cost effects, (C) 2001 Elsevier Science B.V. All rights reserved.