Results from ultrasonography, computed tomography (CT), scintigraphy, hepatic angiography, and magnetic resonance (MR) imaging were analyzed for five patients with surgically proved fibrolamellar hepatocellular carcinoma (FL-HCC)--a variant of hepatocellular carcinoma (HCC) that usually occurs in younger patients and has an improved prognosis and chance for curative resection. The radiologic findings were generally inconclusive for a differential diagnosis because the appearance of the lesions on the various imaging studies closely simulated that of either focal nodular hyperplasia, HCC, or metastases. CT and technetium-99m sulfur colloid scintigraphy were the most effective techniques for the workup of these lesions, but because they do not allow a definitive diagnosis, open biopsy is recommended for most lesions simulating focal nodular hyperplasia and HCC in younger patients. Although the current specificity of MR imaging in diagnosing liver lesions is low, further experience may permit more specific characterization of these lesions.