Radiofrequency ablation and irreversible electroporation are both interventional procedures used in treating cancer diseases generally and may be used in treatment of liver cancer. The two differ in terms of their action and thermal effects. The present study examined thermal effects of radiofrequency ablation and modified irreversible electroporation ex vivo in porcine liver. Standard radiofrequency ablation was used during the experiments, as was a unique, experimental high-voltage generator of the research team's own construction coupled with a newly designed balloon electrode catheter for irreversible electroporation. The tested balloon catheter was newly designed for application in the biliary tract. The temperature of porcine liver tissue was monitored without contact by infrared camera. The results show significantly different temperature of tissue around electrodes for radiofrequency ablation and irreversible electroporation. The data obtained from radiofrequency ablation with maximum tested output power of 10 watts show a symmetrical area of tissue near active electrodes with temperature increased by more than 30 °C. Irreversible electroporation methods showed temperature increasing approximately by 5 °C. To summarize, the thermal research showed that the difference between standard RFA and innovated IRE with the balloon catheter lies not just in the differing mechanism of action, as is well known, but also in its thermal effects. There was documented that tissue temperature was much higher for RFA than for IRE, particularly for the maximum tested output parameters. The applicability of the newly designed balloon catheters was confirmed.