During recent years, there has been an increasing interest in the evaluation of the food-processing side streams, due to their potentially valuable phytochemical content. Olive mill waste water (OMWW), the main by-product of the olive oil extraction process, is rich in polyphenolic compounds, widely known for their health-promoting benefits. However, different parameters--such as the distinct olive cultivar, ripeness of the fruit, processing techniques, climate, and storage conditions--play an important role in determining the specific quali-quantitative polyphenolic composition of OMWW. In this study we have characterized and compared the polyphenolic profile of two different OMWW from the same Nocellara etnea cultivar, however, they underwent different processing technologies.