For primary liver tumors and selected cases of colorectal liver metastases, surgical resection with preserved oncological margins of healthy tissue has been a method of choice. The criteria that decide about qualifying the patients to surgical resections include the number of nodules, size, localization, infiltrations to vessels or neighboring organs, liver functions, and patient's general condition. In fact, these criteria confine the number of performed resections to 5-25% of cases. These low rates encourage the search for the effective methods of primary and secondary liver tumors destruction with low complication rates. The authors review the results of radiofrequency thermal ablation (RFA) used to treat hepatocellular carcinoma and colorectal metastases in 65 patients, who underwent 178 RFA procedures (143 percutaneous and 35 during laparotomy). Positive response (regression, fibrosis or stabilized disease) to RFA was obtained from 60% of cases, and 3 (1.7%) patients developed bowel perforation. RFA is recommended as effective method with low rates of complications to be used for palliative treatment of unresectable primary and secondary liver malignancies.