Olive leaves represent an easily accessible and inexpensive raw material for the isolation of bioactive compounds. Olive leaf extract is extraordinarily rich in phenolic compounds that have many pharmacological properties, such as antioxidative, anti-inflammatory, antimicrobial and antiviral properties. Oleuropein, as the most common compound in the extract, belongs to secoiridoids and in addition to the above mentioned properties, exhibits cardioprotective and neuroprotective effects, functions as a vasodilator, reduces cholesterol levels and protects the organism from cognitive decline. The purpose of this study is the extraction, isolation and quantification of oleuropein, tyrosol, 3-coumaric acid, para-hydroxyphenylacetic acid, 3-hydroxytyrosol and pinoresinol from three varieties of olive leaf (Drobnica, Buţa (Labin) and unknown variety (Umag)) from the area of Istria. Qualitative and quantitative analysis of olive leaf extract was performed using Ultra-high performance liquid chromatography (UHPLC).The specific aim was to examine the influence of solvent and temperature on the extraction (80% ethanol extraction at 70 °C, 80% ethanol extraction at 78 °C (reflux) and extraction with distilled water at 90 °C, for a period of 4 hours) on the concentration of phenolic compounds in olive leaf extract, and determine which extraction technique results in their highest concentration, as well as from which olive variety. The obtained results have shown that the concentration of phenolic compounds in olive leaves varies and depends on the variety (genetic basis), the age of the olive tree and the applied extraction method. The highest concentrations of oleuropein and pinoresinol were obtained using the 80% ethanol as a solvent at a temperature of 70 °C, while the highest concentrations of 3-hydroxytyrosol and tyrosol were obtained by extraction with distilled water at the temperature of 90 °C, in all three varieties. The highest oleuropein concentration is 35,28 mg/g obtained from old unknown olive variety from the Umag area, and the highest concentration of 3-hydroxytyrosol was obtained in the Drobnica variety, a old varietal olive leaf from the Labin area, amounting to 2,91 mg/g. The toxicity and safety of solvents used in extraction represent a problem in using such extracts as dietary supplements, as well as therapeutic and cosmetic products for human consumption. Therefore, ethanol and water have been used in this study so that obtained extracts could be used to improve human health. In future research it is necessary to optimize the extraction methods and to fully examine the potential therapeutic effect of identified components on human health, in vitro and in vitro.