Preliminary reports showed that contrast-enhanced intraoperative ultrasonography (CEIOUS) provides information on primary or metastatic tumors of the liver that is not obtainable with conventional intraoperative ultrasonography (IOUS). This study validates the impact of CEIOUS, focusing on resective surgery for colorectal cancer (CRC) liver metastases. Twenty-four consecutive patients underwent liver resection using IOUS and CEIOUS for CRC liver metastases. CEIOUS was accomplished with intravenous injection of 4.8 mL of sulphur-hexafluoride microbubbles. CEIOUS found lesions missed at preoperative imaging and at IOUS in four patients and confirmed all of the new findings of IOUS in four patients. In addition, CEIOUS helped to define the tumor margins of the main lesion in 29% of patients with CRC liver metastases. No adverse effects were observed in relation with CEIOUS. In conclusion, CEIOUS improves IOUS accuracy with a significant impact on surgical strategy and radicality in patients who undergo surgery for CRC liver metastases.