After pruning olive trees, a significant amount of waste is generated in the form of leaves and branches, which are rich in polyphenols. As part of this thesis, dry extracts were prepared from olive leaves, branches with leaves, and branches without leaves. The plant material was air-dried and then stored at room temperature and at 4°C for three months before extraction. After extraction using an ultrasonic bath and preparation of dry extracts, the total polyphenol content (TPC), o-diphenol content (o-DPC), and total flavonoid content (TFC) were analyzed using the UV-Vis method, while oleuropein (OLE) was analyzed using the HPLC method. The content of these compounds in the dried samples stored at room temperature and ones at 4°C was then compared. The leaf extract prepared from leaves stored at 4°C had the highest OLE content, 30.7 mg/g of dry extract (DE), and the results expressed per dry plant material (DW) showed the highest OLE content in leaves stored at 4°C, 2.88 mg/g DW. The TPC and TFC content was highest in the extract from branches without leaves stored at 4°C, with values of 193 mg GAE/g DE and 82.9 mg CE/g DE, respectively. Results expressed per DW showed the highest content in leaves stored at 4°C, with TPC values of 14.1 mg GAE/g DW and TFC of 5.99 mg CE/g DW. The o-DPC content was highest in the leaf extract stored at 4°C, 150 mg GAE/g DE, and in leaves at 4°C, 14.1 mg GAE/g DW. This study showed that the storage temperature of plant material affects the values of TPC, o-DPC, TFC, and especially OLE, whose content was nearly half as low in samples stored at room temperature.