He present work was aimed at investigating the composition and content of phenolic compounds contained in polymorphic plants Polygonum aviculare L. (Polygonaceae) of geographically distant populations using the method of high-performance liquid chromatography (HPLC). Research materials included leaf samples collected during the flowering period across the regions of Novosibirsk, Irkutsk and Murmansk, as well as the Republics of Khakassia, Buryatia and Altai. Waterbath extraction was performed in 70% ethanol for the purpose of extracting phenolic compounds (flavonoids and phenolic acids). The composition of the phenol complex was analysed by an Agilent 1200 liquid chromatograph equipped with a diode matrix detector. The plants under investigation are found to contain the following phenolic compounds: flavonol glycosides, such as juglanin, hyperoside, avikularin, quercitrin, aglycones quercetin, kaempferol and myrsetin; C-glycosides of flavones - orientin and vitexin; ferulic and other acids. The first group consisting of 8 samples predominantly featured juglanin (3,6 mg/g) and hyperoside (3,0 mg/g), while 4 samples in the second group mostly contained avcularin (4,9 mg/g). The major component in plants from two distance populations was flavonol glycoside quercitrin (2,2 mg/g). Ferulic acid (1.6 mg/g) was found only in plants comprising the first group. Therefore, phenolic compounds contained in Polygonum aviculare are shown to be characterized by a high biochemical variability in terms of composition and content. At the same time, no correlation has been found between the qualitative composition of phenolic compounds in the plants under study and their habitats.