The objective of the study was to investigate the impact of particle size reduction degree of high-fibre preparations on their functional properties e.g. water binding capacity and cation exchange capacity. Wheat bran (PS), cocoa husks (KA), sugar beet pulp (BC), apple pomace (JA), black chokeberry pomace (AR), black currant pomace (CP), and corncobs (KU) with a particle size of 50 μm and 10-20 μm constituted the material for investigations. The preparations investigated were characterized by varying water binding capacity. The BC preparation with a particle size of 50 μm showed the highest water binding capacity (9.17 g H₂O/1 g dietary fibre), and the AR and KU preparations with a particle size of 10 – 20 μm – the lowest, i.e. 2.90 g H₂O/g dietary fibre and 3.18 g H₂O/g dietary fibre, respectively. The higher degree of particle size reduction the lower was their water binding capacity. The degree of particle size reduction influenced the cation exchange capacity in a diversified way. The KA preparation with a particle size of 10 – 20 μm (0.272 mEq/g dietary fibre) showed the highest cation exchange capacity, and the PS preparation with a small reduction size (50 μm) – the lowest, i.e. 0.004 mEq/g dietary fibre.