Flavonoids in commerical green-yellow vegetables (carrot, mugwort, perilla leaf, leek and water dropwort) were analyzed by HPLC. Flavonoids analyzed in samples were myricetin, luteolin , qercetin, apigenin and kaempferol. When 2N HCI and a reaction period of 1 hours was used, quercetin and kaempferol could be detected in leek and water dropwort, luteolin and apigenin could be detected in perilla leaf. Increasing reaction period up to 6 hours with 2N HCI led a degradation of quercetin and kaempferol to approximately 90% in leek and water dropwort, but it led to a increasing of luteolin and apigenin of maximum 300% in perilla leaf. After the blanching process, the amount of the flavonoids increased whereas the components of the flavonoids were not changed.