Consummation of the virgin olive oil as a final spice or in the cooked food is rising in the world, mainly due to the proven nutritional benefits. After extraction, virgin olive oil contains most of the olive fruit components, namely pigments, phenolic and volatile compounds. However, after thermal treatment, nutritional value of oil is often examined. In this study oil extraction from Leccino olive variety was carried out in two ways. The first oil extraction was made only from olive fruit, while another from the olive fruit and olive seeds. All oil samples were subjected to the thermal treatment at 170 °C for 8- and 12-hour exposure. After thermal treatment the antioxidant capacity of oil samples as well as kinetics of the chemical reactions between DPPH radicals and antioxidants presented in the oil was analyzed. Antioxidant activity was tested using a spectrophotometric method while kinetics of the chemical reactions was analyzed using three monophasic and one biphasic mathematical models. Results of the study showed that the antioxidant capacity of oil samples is weaker during the longer oil temperature exposition and that rate of chemical reaction between the DPPH radicals and the content of the oil is more intense at the beginning of the reaction but decreases during the time. Further, it has been proven that the kinetics of DPPH disappearance is a two-step process; first rapid, followed by a slow decline in the second step. According our obtained results about biphasic kinetics reaction the use of first-order double.exponential model is recommended because it provides immediate and detailed information on antioxidant potential of the oil. Our results were confirmed by obtained statistical indices showing the highest values of the correlation coefficient and the lowest values of SRMSE and 𝜒2 errors. The results of the study indicate that the long-term exposure of olive oil to high the temperature has a negative effect on its quality