Determination of free phenolic compounds in potato samples was optimized using a high-performance liquid chromatographic (HPLC) method with on-line diode array detection. This method was applied to samples of four cultivars of potatoes harvested in Tenerife (Canary Islands). The free phenolic compounds found in the potato samples were (+)-catechin, chlorogenic acid, caffeic acid, p-coumaric acid, and ferulic acid. Potato samples belonging to Colorada cultivar, ssp. andigena, had mean concentrations of total phenolic compounds and chlorogenic acid higher than those found for Kerr's Pink and Cara cultivars, ssp. tuberosum, and for Negra cultivar, S. x chaucha. In contrast, p-coumaric acid was not detected in any potato samples of the Colorada cultivar. Traditional potatoes presented a higher mean concentration of ferulic acid than recently imported potatoes. A significant and negative correlation was established between (+)-catechin and p-coumaric acid. A considerable contribution to the daily intake of flavonoids was observed with the actual consumption of potatoes.