The studied seeds of three Silphium species (Silphium perfoliatum L., Silphium trifoliatum L. and Silphium integrifolium Michx.) contained (recalculating onto dry matter): up to 33.5% of protein, up to 24.1% of fat, up to 9.58% of water-soluble sugars, and up to 25.4% of cellulose. Ash was up to 6.8% of seeds dry matter. Mean energetic value of the analysed raw materials ranged from 1076 kJ/100 g (S. trifoliatum) to about 1530 kJ/ 100 g DM (S. perfoliatum). Mineral element content, particularly K (from about 1.6 g/100 g to about 1.8 g/100 g DM), Ca (from about 1.0 g/100 g to about 2.1 g/100 g DM) or Mg (from 651 mg/100 g to 672 mg/100 g DM) as well as that of trace elements, e.g. Fe (from about 28 mg/100 g to about 38 mg/100 g DM) in Silphium seeds is one of the most important traits affecting their nutritional value. Moreover, the experiment revealed that S. perfoliatum was the most valuable plant referring to seed yielding (about 185 g seeds from a single plant, on average). Glutamic acid (up to 23%) and leucine (7.76%) were found dominating among all amino acids in protein of Silphium seeds. An analysis of lipid fraction showed that linoleic (44.4%) and oleic (13.2%) acids were the main fatty acids contained in the oil made from seeds. The achieved data point out that the analysed raw materials were characterized with a valuable chemical composition and may be used in the food industry.