In the course of chemotaxonomic study of the genus Prunus, seven flavonol glycosides were isolated from the leaves of Prunus serotina Ehrh., characterized by UV and NMR spectroscopy, and identified finally as three quercetin monosides: hyperoside, avicularin, reynoutrin, three quercetin biosides: 3-O-(6"-O-alpha-L-rhamnopyranosyl)-beta-D-glucopyranoside, 3-O-(2"-O-alpha-L-rhamnopyranosyl)-beta-D-glucopyranoside and 3-O-(2"-O-alpha-L-rhamnopyranosyl)-beta-D-galactopyranoside as well isorhamnetin 3-O-(6"-O-alpha-L-rhamnopyranosyl)-beta-D-glucopyranoside. The presence of determined flavonoids in the flowers was confirmed by TLC.