Echinococcosis is a very common parasitic infection in animals, but in humans is quite rare. The long symptomless period obstructs early diagnosis. Symptoms usually appear after many years of infection and they are not very characteristic. It causes delay of correct treatment and decreases the chances of saving the patient’s life. Echinococcosis is an extremely dangerous disease and can cause severe, long-term and very often irreparable complications, even loss of the patient’s life. Echinococcosis is caused by larval stages of cestode species of the genus Echinococcus . The life cycles of these parasites involve two mammalian hosts: the definitive host (usually a carnivore) and the intermediate host (humans are aberrant hosts). In Poland, cystic echinococcosis (CE) caused by Echinococcus granulosus and alveolar echinococcosis (AE) caused by Echinococcus multilocularis have been observed. Usually it is localized in the liver, the lung and the brain. The diagnosis of echinococcosis in individual patients is based on identification of cyst structures by ultrasonography, computed tomography, X-ray examinations, magnetic resonance imaging and the confirmation by detection of specific serum antibodies by immunodiagnostic tests. Final diagnosis is based on confirmation of hooks and protoscoleces in cyst fluid and the examination materials from the operation. There are several major options for treatment of echinococcosis, including surgery, puncture aspiration injection respiration (PAIR), and chemotherapy (albendazole, mebendazole).