Hypothesis: Positron emission tomography (PET) influences clinical management in the preoperative evaluation of patients with hepatic metastases from colorectal cancer. Design: Prospective cohort study. Setting: Academic tertiary care center. Patients: From January 1, 2000, through December 31, 2002, 71 consecutive patients referred with potentially resectable hepatic metastases based on conventional imaging findings underwent PET or PET with computed tomography in the subsequent preoperative evaluation. Intervention: Performance of hepatic resection was based on the results of the overall preoperative evaluation. Main Outcome Measures: Concordance with conventional imaging findings, identification of additional findings, and change in clinical management were analyzed. Results: The PET findings confirmed the lesions identified by conventional imaging techniques in 64 (90%) of the patients. Additional lesions were identified on PET in 23 patients (32%). The information obtained by PET resulted in a change in clinical management in 17 cases (24%). False-positive PET findings occurred in 6 patients (8%), whereas false understaging occurred in 11 (15%). In no cases did PET findings have an adverse impact on patient outcome. Conclusions: Postiron emission tomography provides useful information in the selection of patients with hepatic metastases from colorectal cancer being considered for surgical therapy. Such improved selection may serve to reduce the number of unnecessary surgical explorations and result in improved long-term survival in patients undergoing resection. Positron emission tomography should be integrated into the routine preoperative evaluation of patients being considered for hepatic resection of colorectal metastases.