The studies aimed to evaluate the significance of cereal products as an essential source of Ca, Mg and K in the diets of Poles. The study covered 226 groups of cereal products most popular in Poland: bread, bread rolls, cooked pasta, cooked grains and cooked rice. The content of Ca, Mg and K was determined by means of FAAS. In addition, considering the recommended daily intake of K, Ca and Mg for the Polish population of adults, the percentage share of respective products in daily supply of these minerals was determined. The content of the above-mentioned minerals in all analysed cereal products can be presented as K > Mg > Ca. Intake of cereal products covers the requirement of K, Mg and Ca among adult Poles, respectively, in ca. 9%, ca. 12 (men)–15 (women) % and ca. 3%. The best source of K, Mg and Ca is bread which in the daily diets of Poles supplies more than 90% of minerals consumed with cereal products. It can be claimed that cereal products are a poor source of Ca, but they supply significant amounts of K and Mg in the diets of Poles, especially given that deficiency of such minerals is common in Poland. It would be important to consider obligatory fortification of flour with minerals which are deficient in the diets of Poles.