The composition of phenolic compounds of leaves of Spiraea aquilegifolia Pall. in comparison with S. hypericifolia L., another Siberian species of the section Glomerati Nakai, was studied for the first time. Differences between the two species were not revealed. In the extracts of leaves of S. aquilegifolia and S. hypericifolia at least 31 compounds were revealed, including six flavonoids, 4 of them were identified as hyperoside (0.38 % and 0.12 %, respectively), isoquercitrin (0.15 % and 0.54 %), aviсularin (0.23 % and 0.15 %) and rutin (0.02 % and 0.03 %). The dominant components of both species are chlorogenic, p-coumaric acid, hyperoside, isoquercitrin and aviсularin. The maximal number of components was found in the extract of S. aquilegifolia from Mukhorshibirsky District of Buryatia (near the place Kusoty). In the hydrolysates of S. aquilegifolia and S. hypericifolia more than 27 compounds were identified, including two flavonoids. The content of total phenolic compounds was detected (up to 4.83 % and 6.4 %, respectively), including flavonoids (up to 1.86 % and 1.09 %). Over 90 % of flavonoids of hydrolysates of both species was quercetin. Variability of composition of phenolic compounds of populations was low (similarity ca. 90–100 %).