Provided are immunoconjugate probes useful for detecting hepatocellular carcinoma (HCC) lesions. The probes comprise a glypican-3 (GPC3)-specific monoclonal antibody or fragment thereof conjugated to a radionuclide such as 89Zr, 64Cu, and the like. The probes are useful for obtaining PET images with high tumor-to-liver ratios and targeting for diagnostic imaging of HCC lesions or cells in vitro and in vivo.
