The qualitative and quantitative compositions of flavonoids (vicenin-2, luteolin-3′-di-O-glycoside, luteolin-7-O-glycoside, rutin, apigenin-7-O-glycoside, luteolin, apigenin) and chlorogenic acid in herb, leaves, and stems of yarrow (Achillea millefolium) samples collected in the Kaunas region of Lithuania have been studied by means of high-performance liquid chromatography (HPLC). It is established that these substances exhibit a characteristic distribution with predominant formation of apigenin-7-O-glycoside and luteolin-7-O-glycoside among the identified flavonoids in the herb of yarrow whereas the leaves contain predominantly chlorogenic acid, rutin, and apigenin-7-O-glycoside; the stems, predominantly chlorogenic acid, rutin, apigenin-7-O-glycoside, and luteolin-7-O-glycoside. The results can be used to choose selection donors of this medicinal plant material.