Results of orcein staining and findings obtained with non-contrast-medium-enhanced computed tomography (CT) and magnetic resonance (MR) imaging (T1- and T2-weighted images) were compared for 53 histologically confirmed hepatocellular carcinomas (HCCs). HCCs were 5 cm in the largest diameter. Three lesions with diffuse and strong orcein staining were highly attenuating on nonenhanced CT images. Electron x-ray microanalysis of one of them revealed copper. The high attenuation value at nonenhanced CT may have been due to the abundant copper-binding protein in the cancer cells. The difference between orcein staining results and attenuation patterns at CT was statistically significant (chi 2, P less than .001). It could not be concluded that the paramagnetic effects of copper in HCC had an influence on signal intensity on MR images. The difference between orcein staining results and signal-intensity patterns on T1- and T2-weighted images was not statistically significant.