Buckwheat hulls (BWH) are a lignocellulosic material with valuable nutrient contents, especially rutin and dietary fibre, which are worth exploring from a food industry perspective. BWH are also a voluminous material that is difficult to grind to very fine particle sizes, which can be achieved under cryogenic conditions. Therefore, we investigated the effect of fractionation by cryo-grinding and size separation (<56, 56-180 and >180µm) on the dietary fibre content and bioactive profile of BWH. While we hypothesised that micronisation would increase fibre solubility and release of bioactive compounds, we found that BWH must be fractionated to a size <56µm to show a significant increase in soluble fibre content (106%), rutin (66%), total free phenolic compounds (94%) and antioxidant capacity (45-63%). Moreover, we have shown that near-infrared spectroscopy combined with partial least squares regression can be easily used for rapid scanning of BWH to select the most suitable pre-processing conditions for maximum nutritional value of this food industry by-product. © 2021 Institute of Food Science and Technology.