The diagnosis of cardiac hydatid disease is a difficult one. Conventional and specific cardiac investigations are not pathognomonic of this disease. In this report, the diagnostic value of computed tomography (CT) scanning was prospectively investigated in seven patients. In five patients, the diagnosis was confirmed surgically. The CT-information obtained correlated accurately to the operative findings. In all the patients, CT-densities of the lesions were measured and were found to coincide with values of mean CT-densities of hydatid cysts elsewhere in the body. The capability of measuring tissue densities is unique to CT-scanning and have been emphasized in this report.