The objective of the study accomplished was to determine the influence of technological treatment procedures applied to manufacturing buckwheat groats on the content of protein, lipid, saccharides, and uronic acids in the grains of buckwheat and of roasted buckwheat groats. The technological process comprised the following phases: cleaning, roasting (130 °C during 1 h and saturation with water vapour during 15 min.), seasoning (24 h), sorting out I, dehulling, sorting groats out, removing hulls, sorting out II: packing, distribution. The samples investigated were: grains of buckwheat, grains of roasted buckwheat, whole buckwheat groats, and broken buckwheat groats. The scope of the analysis performed included: total protein, total lipid, saccharides: saccharose, glucose, galactose with fructose, arabinose., and the content of glucuronic and galacturonic acids. The content of protein was determined using a Kjeldahl method and a Kjeltec set of devices manufactured by the ‘Tecator’ Co. in Kielce (Poland); the content of lipid was determined using a Soxtec HT6 apparatus manufactured by the ‘Tecator’ Co. The saccharides and uronic acids were determined using a liquid chromatography (HPLC). The results obtained suggest that the technological process applied impacts the change in the content of the selected nutrients. The content of protein in the caryopses/grains/grains of buckwheat, in the grains of roasted buckwheat groats, and in the whole buckwheat groats was higher than in the broken groats. The content of total lipid in the grains of buckwheat prior to and after roasting, and in the buckwheat groats remained at the same level, however, it decreased in the broken buckwheat groats. It was found that the content of saccharose increased, but the levels of glucose, galactose with fructose, and arabinose decreased in the grains of buckwheat after roasting, in the broken buckwheat groats, and in the whole buckwheat groats if compared with the buckwheat grains prior to roasting. The technological process did not impact the content of uronic acids.