The aim of the present paper was quantitative evaluation of inulin occurring in rhizomes and roots of Silphium perfoliatum L., Silphiu m trifoliatum L. and Silphium integrifolium Michx. (Asteraceae). It was found that all studied underground organs contained inulin. It was proven that rhizomes of Silphium trifoliatum L. contained the highest amount of inulin (up to about 38% DM). Moreover, the experiment revealed that the percentage content of fructose in Silphium inulin amounted from 71% to 94%.