FDG-PET imaging has an important role in determining if there are metastases to the liver and whether disease has spread beyond the liver. Such information is critical for planning surgical resections of liver metastases. Although FDG-PET can fail to detect many HCCs, it does detect many of the poorly differentiated ones and other PET tracers are showing promise for the detection of better-differentiated hepatomas. Although low-volume CC can escape detection by FDG-PET, higher-volume lesions are well detectable. Similarly, GBC is generally well detected by FDG-PET. The ability of FDG-PET quantitatively to estimate metabolic rates makes it an important tool for monitoring. With increasingly broad indications for FDG-PET imaging, it is expected that FDG-PET (and PET-CT) of the liver will play a growing and increasingly important role in detecting and monitoring treatment of tumors involving the liver.