The main aim of this study was to compare the thermal resistance of virgin olive oils of the Leccino cultivar obtained from whole and de-stoned fruits. Virgin olive oils were subjected to a stimulated frying process that is heating without the presence of the food at 170 °C for a total duration of 12 hours. In heated oils, changes of specific UV absorbances (K232 and K270 – indicators of oxidative degradation), mass fraction of total phenolic compounds and chlorophylls, were determined spectrophotometrically. Considering percentage of free fatty acids and the K-values, oils used for heating were extra virgin. It was found that the olive processing significantly influenced the degree of oxidation, mass fraction of total phenols and chlorophylls in oil. The oil obtained from de-stoned fruits had statistically significantly lower values of K232 and K270, a higher mass fraction of phenolic compounds and lower total chlorophylls compared to the oils from the whole fruit. During the oil heating, the degradation of primary oxidation products is faster than their formation, which is indicated by changes of specific UV absorbances (because of their high values after 4 hours of heating, these oils became inedible or "lampante"). Oil heating during 12 hours caused oxidative degradation of phenolic compounds and chlorophylls, and reduction of their total mass fraction: by 12% and 57% in oils from the whole fruits, and by 20% and 73% in de-stoned oils, respectively. Although, de-stoned oil samples had lower initial oxidation degree and higher mass fraction of phenolic compounds, after 12 hours of heating they had more deteriorated nutritive properties than whole fruit oils.