Aucklandia lappa Decne (Compositae) has been used for treatment of vomiting, diarrhea, abdominal pain and indigestion and Inula helenium L. (Compositae) for sweat and urination. In spite of difference species and efficacy, we have been used Aucklandia lappa Dence together with Inula helenium L. To distinguish Aucklandia lappa Dence from Inula helenium L., we have compared the contents of dehydrocostuslactone and costunolide by HPLC. The average contents of costunolide of Aucklandia lappa Dence was 0.84% $({pm};0.29)$ but was not detected in Inula helenium L. The contents of dehydrocostuslactone from Aucklandia lappa Dence and Inula helenium L. were about 1.70% $({pm}0.37)$ and 1.82% $({pm}0.59)$, respectively.