Nine patients with cystic or necrotic hepatic neoplasms had findings on computed tomography (CT) that strongly suggested benign cystic disease of the liver. Sonography depicted the true morphology of these cystic lesions more clearly than CT, and the sonographic findings virtually excluded uncomplicated hepatic cyst as a diagnosis. Important observations were wall thickness, mural nodules, septations, and fluid-fluid levels. The potential danger in over reliance on CT attenuation values and the complementary role of sonography and CT in such cases are stressed.