In the diploma thesis, we presented the all-too-often ignored buttermilk, a liquid by-product obtained by churning of either sweet or sour cream into raw butter. However, as the name buttermilk also describes various dairy products, which differ by the area and method of production, our thesis mainly focused on the traditional sweet and sour buttermilk, which are dairy products known in the Slovenian territory. We also presented its composition and nutritional value. The neglect of traditional buttermilk among dairy products is probably due to its poor recognition and uncompetitive struggle in the harsh dairy market which is stuffed with fermented milks that promise health benefits due to various additives and composition such as probiotic bacteria, high protein content, lactose-free, reduced or no fat content. Nevertheless, most of listed characteristics are buttermilk’s attributes by its nature, where especially its composition and nutritional value are the qualities that speak in favour of its greater recognition and importance in the future. Among others, it contains phospholipid lecithin, which is attributed to its beneficial physiological effect on the human nervous system. Fermented buttermilk is a good source of calcium, phosphorus, vitamins B2, B12, pantothenic acid, and other nutrients, which make buttermilk a nutritious and healthy drink. Buttermilk is used as an additive in the production of yogurts, cheeses, as a nutrient medium in microbiological analysis of microorganisms. It is also well known in the manufacture of low-fat cheese and yogurt. Buttermilk powder is mostly used in the bakery industry. In households, this by-product obtained at raw butter production can be used in many ways. In our work, we presented its use in baking pastries.