Computed tomography (CT) findings in hydatid disease (echinococciasis) of the liver are described. Disease was caused by Echinococcus granulosus (n = 8) or E. alveolaris (n = 5), respectively. The CT appearance of these two types of echinococciasis is quite different: in disease caused by E. Granulosus the CT appearance is pathognomonic when cysts and daughter cysts surrounded by a capsula and peripheral calcifications are discernible. In addition, the extent of organ involvement can be determined prior to surgical intervention. The CT appearance of E. alveolaris lesions may be indiscernible from malignant tumors.