Purpose: To study and define the opportunities of intraoperative ultrasound examination (IOUS) in the contemporary diagnostics and the treatment of hepatocellular carcinoma (HCC). Patients and Methods Used: This is a prospective study for the period 2007 – 2013 of 40 patients who had undergone an open operative inervention for hepatocellular carcinoma. The engaging of the liver by the tumor process is examined preoperatively with percutaneous ultrasound examination (US) and computer tomography with contrast amplification (CT) and during the surgical operation – with inspection and palpation and IOUS. The number and localization of the hepatic lesions are compared to the preoperative results and the focal changes are verified histologically. Results: IOUS found malignant hepatic lesions which were not found by US and CT in 10/40 patients (25%). Most of them were measuring up to 2 cm - 19/25 (76%). The additional information from IOUS led to change of the operative plan in 13/40 of the patients or 32,5%. Besides with the help of this examination the malignant lesions were localized exactly on the amatomical segments of Couinaud. Conclusions: The routine use of IOUS in patients with primary hepatic tumors emhances the detection of malignant hepatic lesions as well as helps the surgeon to choose the suitable strategy during the operation. The use of IOUS is particularly valuable in patients with HCC and cirrhosis of the liver, where the precise defining of the localization of the tumor and its interrelations with the hepatic vessels allows an economical resection to be performed and securing adequate borders of the removed by the resection tumor.