Widely distributed in plants, flavonoids reduce the incidence of cancer and cardiovascular disease. In this study, flavonoid content and composition in members of the genus were evaluated using liquid chromatography with diode array and electrospray ionization mass spectrometric detection (UPLC-DAD-ESI/QTOF-MS). Flavonoids in plants of the genus include the basic structures of kaempferol, quercetin, and catechin, and exist as mono-, di-, or tri-glycoside compounds mono-acylated with acetic acid. A total of 23 individual flavonoids were isolated and confirmed, three of which appear to be newly identified compounds: quercetin 3--(2″--acetyl)neohesperidoside, quercetin 3--(4″--acetyl)rutinoside, and kaempferol 3--(4″--acetyl)rutinoside. Japanese apricot and Chinese plum contained the highest amounts of flavonoids in the genus. During the ripening stage of Japanese apricot, the total flavonol content was reduced, while the catechin content was increased.