Flavonoids have been of considerable importance and interest because of their medicinal activity. Responding to their numerous health benefits, a comparative study on the quantitative determination of total polyphenolic compounds and flavonoids was carried out in Achillea millefolium and Equisetum arvense. Total polyphenolic compounds were quantified by Folin-Ciocalteau method using different solvents in order to prove their extraction efficiency. Focus within total polyphenolic quantification study was placed on the traditional reflux and solvents used were: water, 100% acetone, 100% ethanol, 80% ethanol, 50% methanol and 70% methanol. In order to make flavonoids free from glycosidic moiety for quantification, hydrolysis was performed in 50% MeOH at 90°C using 6 M HCl concentration. Reverse phase high performance liquid chromatography (RP-HPLC) in gradient elution mode at 50°C using Hypersil BDS (RP-18) column was employed for the separation of flavonoids. Mobile phase used consisted of different combinations of water-methanol-tetrahydrofuran-phosphoric acid. Flavonoids quantified were luteolin, quercetin, apigenin, isorhamnetin and kaempferol.