The purpose of this retrospective study is to clarify the clinical, radiological and evolutionary aspects of the hydatid cyst of the lung. Over a period of 9 years (January, 1983 - December, 2001), we brought together in the pediatric service B of Children's hospital of Tunis, 54 cases of hydatid cyst of the lung. The average age is of 7 years 3 months (extremes 2 and 14 years), and the sex- ratio of 1,16. 61% of the children are of rural origin. Bronchpulmonary infection is the most frequent circumstance of discovery (72 % of cases). hemoptysis is revealing in 37% of cases. Discovery is fortuitous in 7% of cases. The radiography of the chest is of a big diagnostic contribution. The radiological aspects obtained are: a homogeneous opaqueness (61%), a diverse opaqueness (26%), an image of lung abscess (22 %), an aspect of floating membrane (4 %), a pleural effusion (9%), and an opaqueness with growing gas (4%). Chest echography was contributory in 77% of cases. 74% of the children were operated without complications. The others were lost.