The sugar content in the grits and in a gruel cooked with samples of oats and buckwheat subjected to hydrothermal treatment under different conditions and also in the oat flour, a product of baby and dietetic nutrition, was quantified. Hydrothermal processing results in significant changes occurring individual sugars of the grit. During culinary treatment these changes are levelled out, but in the end the level of virtually all types of sugar is higher in the gruel cooked with hydrothermally treated grit than in that prepared with initial, untreated grit. The oats flour is distinguished by a high glucose, maltose, fructose and saccharose content. A fall of the reducing sugars level coming as a result of thermal and culinary treatment is explained by their participating in the reaction of melanoidine formation. On the other hand, a rise in their content under rigorous conditions and in the production of oat flour is due to the starting of the starch hydrolysis.