Hydatidosis in humans is a parasitic disease produced by cystic growth of the larvae of the tapeworm Echinococcus granulosus, affecting mainly the liver and lung. Larvae are rarely present in the mediastinum, although approximately 100 cases have been described in the literature. We report eight cases of hydatid cysts of the mediastinum (HCM) treated surgically over a period of 21 years. The incidence was similar in males and females and ages ranged from 10 to 74 years. Symptoms depend on size, location and involvement of neighboring structures in HCM. The most serious complication is cyst rupture with consequent transfer of hydatid material to the blood, possibly causing anaphylactic shock and even death. Currently, sonography, computed tomography and magnetic resonance images facilitate diagnosis. Treatment involves excision of the cyst and peri-cystic tissue. CHM should be suspected when mediastinal cysts are found in countries where the incidence of hydatidosis is high.