Disposal of olive mill by-products is associated with several environmental problems in the Mediterranean area where the cultivation of olive trees is extensive. Indeed, olive oil production generates large volumes of wastes with the composition depending on processing conditions, agricultural specificities and season. Nevertheless, olive oil wastes also represent a promising source of bioactive phenolic compounds, well known for their health benefits in terms of antioxidant and anti-inflammatory properties. To reduce the environmental impact of olive oil production and promote the industrial development of olive phenols, efficient methods for the fractionation of olive oil by-products and the analysis of their phenolic composition must be developed. This mini-review focuses on one of the most efficient methods for the structural analysis of olive phenols, i.e. liquid chromatography coupled with a diode array detector and up-to-date mass spectrometry.