Soxhlet extraction, ultrasound extraction, and accelerated solvent extraction (ASE), followed by RP-HPLC with a photodiode array detector was used for the determination of flavonoids in fruits of Peucedanum alsaticum. Three compounds were identified: a kaempherol derivative (astragalin), and two quercetin derivatives (quercitrin and hiperoside). The highest extraction yields of the selected compounds were obtained by use of exhaustive ASE.