The flavonoid composition of three phenotypes of "Zolfino" landraces, a typical bean grown in Tuscany, has been elucidated by means of HPLC-DAD and HPLC-MS analysis. Flavonols, isoflavones, and anthocyanins have been separated and determined in the different samples chosen on the basis of their seed coat color. A flavonol that has not been previously found in Phaseolus vulgaris L. seeds has been characterized. The quantitative data show the presence of flavonols (ranging from 709 to 118 mg/kg of fresh weight), isoflavones (ranging from 14 to 2 mg/kg of fresh weight), and anthocyanins, in black beans only. These results show that this genotype could be very interesting from a nutritional point of view.