Dark-seeded double improved Polish rape seed varieties (Brassica napus L.) (38 samples) were included in this study, with the main purpose of investigating their dietary fibre (DF) components. The chemical composition of unprocessed defatted seeds was determined, including analyses of neutral (NDF) and acid (ADF) detergent fibre, as well as insoluble (IDF), and soluble (SDF) dietary fibre. In eight samples (four spring type and four winter type rape seed) the prevalent DF fraction was IDF occurring in amounts from 27.6 to 34.0% of dry defatted matter (DDM), while SDF accounted for 3.8 to 6.1% of DDM . Arabinose and galactose were the prevalent monosaccharides in both fractions of DF. The DF fractions were associated with protein which was not digested by pepsin and pancreatin used in the isolation procedure. Protein associated with SDF ranged from 7.6 to 18.1% while protein associated with IDF ranged from 28.4 to 41.5% of the total protein content in rape seed. The amino acid composition of protein associated with IDF differed distinctly from that associated with SDF. Protein bound to IDF had an amino acid composition similar to that of whole rape seed, while protein associated with SDF had an extremely high content of lysine, cysteine, and serine, but a low content of methionine and phenylalanine.