Liver is common place where the cancer occurs primary as well as secondary. Liver resection as a potentially healing method can be performed only in about 20% of patients. Prognosis in group of patients treated non-invasively is bad. Using high frequency thermal ablation which damages the neoplastic tissue in liver may lead to prolongation of life expectancy.The aim of the study was to assess the early results of using the high frequency thermal ablation in patients with primary or secondary cancer.Material and methods. During years of 2001-2007 371 patients underwent the 520 procedures of percutaneous RF thermal ablation under US control. Mean age of patients was 62.47 (19-85 ± 11.63). 175 women and 196 men were treated using this method.Results. There were 10 early complications after thermal ablation (1.92% of procedures, 2.7% of patients). Two of them ended fatal (0.38% of procedures, 0.54% of patients). In seven cases absces formation were observed, one of them was the cause of death due to Clostridium perfingens infection. Cholerrhagia from damaged bile duct in cirrhotic liver caused the peritonitis and subsequent death of patient. Two patients suffered from sub-capsular hematoma of liver. 14 patients also suffered from long lasting pain (more than 14 days).Conclusions. Percutaneous thermal ablation in primary or secondary liver tumors is safe and efficient procedure. Long term follow up will give the knowledge about the real value of the procedure.