For consumers, organic food is the byword for high quality and guarantee of production safety. Therefore, the objective of the research study was the analysis of the basic composition (i.e. dry matter, total protein, crude fat, crude fibre, mineral compounds in the form of total ash and total carbohydrates) of four winter rye cultivars (‘Visello’, ‘Kapitan’, ‘Kondukt’, ‘Dukato’) derived from organic and conventional crops as well as the analysis of the fibre fractions (NDF – neutral detergent fibre, ADF – acid detergent fibre, ADL – acid detergent lignin, HCEL – hemicellulose, CEL – cellulose) and macro- elements (calcium, phosphorus, potassium, sodium) therein. Based on the analysis research, it was found that the content of crude protein in rye grain from organic crops was, on average, 9.4 g/kg of d.m. lower compared to that in the rye grain from conventional crops (p ≤ 0.05). Moreover, the rye grain from organic crops contained significantly lower amounts of: total ash, NDF, ADL, and potassium compared to the rye grain from conventional crops. Also, the rye cultivars analyzed differed from each other. Compared to others cultivars, the grain from the ‘Kondukt’ cultivar contained significantly more crude protein, crude fibre, and Ca. Based on the research performed, it was concluded that the organic farming of winter rye grain had no beneficial effect on its chemical composition.