A chemosystematic study of the subgenus Oporinia of the genus Leontodon (Asteraceae) was performed, using flavonoids and phenolic acids in the flowerheads as diagnostic characters. A total of 44 samples from nine different Oporinia taxa were analyzed. Five luteolin-derivatives (luteolin, luteolin 7-O-beta-D-gentiobioside, luteolin 7-O-beta-D-glucoside, luteolin 7-O-beta-D-glucuronide, and luteolin 4'-O-beta-D-glucoside) and four caffeic acid derivatives (caffeoyl tartaric acid, chlorogenic acid, cichoric acid, and 3,5-dicaffeoylquinic acid) were identified in crude extracts by means of HPLC retention times, on-line UV spectra and on-line MS spectra. Quantification of these compounds was performed by HPLC, using quercetin as internal standard. The data obtained were processed by Principal Component Analysis, resulting in the formation of five different clusters. These clusters were taxonomically interpretable and are in good agreement with the morphologically based system of the genus Leontodon.