Lupin seeds of different species representing diverse varieties of sweet lupin grown in Poland were investigated. The chemical compositions of lupin isolates and amino acid composition of the proteins, as well as the nutritive values were estimated. No significant differences (P⩾0.05) were observed among lupin isolates in their dry matter, crude fibre or alkaloid contents. The highest protein content (465±11g/kg d.m.) was found in seeds from lupins belonging to Lupinus luteus (P⩽0.01), while the highest oil content (ca. 115g/kg d.m.) was found in Lupinus albus (P⩽0.05).All the species examined were characterised by a shortage of methionine, lysine, tryptophan and valine while the level of leucine was satisfactory for most of the species. Yellow lupin was deficient in isoleucine. White lupin was found to be a nutritionally more valuable crop than other species by the standards of nutrition for mature human and animals. Apart from the highest level of amino acids within the crude protein (AA – 97.7g/16 gN, P⩽0.01), it was found to have a better and nutritionally more beneficial amino acid composition and the highest essential amino acids level (EAA). White lupin was characterised by a higher essential amino acid index (EAAI) as well as chemical score (CS) of restrictive amino acids, and the highest protein efficiency ratio (PER), expressed in terms of the availability of leucine and tyrosine as compared to blue and yellow lupin varieties. White lupin, followed by blue and yellow lupin, was found to be suitable for animal feeding as well as for the production of high-protein concentrates for further food processing and use in animal and human nutrition.