Introduction: Hydatid disease is a severe disease caused by Echinococcus, a larvae endemic in many developing countries. Hydatid cysts are usually found in the liver in most cases. These cysts show no symptoms and are discovered accidentally during abdominal ultrasonography. Lungs are the second most common site of hydatid cysts were they can be referred to as pulmonary cysts.

Case Description: A 6-year-old previously healthy boy presented to the pediatric clinic for a one-month history of dyspnea and recurrent episodes of dry cough. CT scan of the chest was performed to reveal a large pulmonary hydatid cyst measuring about (9cm x 7cm). Thoracotomy was done and the cyst was successfully removed followed by a full coarse of Albendazole. Patient had good prognosis.

Discussion: Pulmonary hydatid cyst which is a rare infectious disease usually presents at adulthood due to the slow growing nature of the larvae even when the responsible agent is encountered during childhood. This what gives the uniqueness of the presented case in addition to its very large size.

Conclusion: Surgery which is the gold standard for the management of hydatid cysts must be done as early as possible to avoid complications such as rupture of the cyst. This must be followed by full coarse of albendazole to prevent the recurrence of the infection.

Keywords: Hydatid cyst; Lungs; Echinococcus; Thoracotomy