The extracts from leaves, roots and flowers of Himalayan Knotweed (Persicaria polystachya (Meissner) H. Gross) were analysed by HPLC and CE (capillary electrophoresis). Catechin, quercetin, quercetin-3-rhamnoside (quercitrin), quercetin-3-D-galactoside (hyperoside) were detected.