Colorectal cancer is a major cause of cancer death in Western Europe and United States; the liver is the most common site for colorectal metastases. PET has an important role in the management of patients with colorectal liver metastases. It is an effective tool to detect hepatic metastases and to monitor the response to systemic and local therapy. The major impact of PET-CT over PET alone is the improvement in the certainty of lesion location. PET-CT has the unique advantage to combine functional and anatomic imaging in an integrated scanner; it allows a thoroughly evaluation of patients with colorectal liver metastases.