Aim of the experiment was evaluation of the effect of reduced calcium and magnesium content in the broiler chickens diet on its parameters of fattening, bone strength and calcium and magnesium content in liver. The trial was performed with cockerels of Ross 308 hybrid (n = 160) which were fattened in cage batteries from day 11 th to 36 th day of age. Cockerels were divided into 4 groups (differ in various intake levels of calcium and magnesium) in four replications. The maizewheat-soybean basal diet contained 2.33 g Ca and 1.58 g Mg per kilogram. Calcium was added by CaCO 3 and magnesium by MgSO 4 . Control group (C) received feed mixture with added CaCO 3 in dose of 19.49 g.kg -1 and 0.41 g.kg -1 of MgSO 4 . Three experimental groups contain added CaCO 3 in dose of 11.83 g.kg -1 and 0 g.kg -1 MgSO 4 (group Exp1); CaCO 3 11.83 g.kg -1 and 0.41 g.kg -1 MgSO 4 (group Exp2); CaCO 3 19.49 g.kg -1 and 0 g.kg -1 MgSO 4 (group Exp3), respectively. The feed consumption was daily monitored and the cockerels were weighed twice a week. At the end of the study the experimental animals were weighted and slaughtered by decapitation. The weight of carcasses, liver and proportion of breast and thigh muscle was determined in the selected chickens (n = 24). The atomic absorption spectrometry was used for Ca and Mg evaluation in liver tissues. Bone strength parameter was measured at the femur bone. The statistically significant differences (p >0.05) were not detected between control and experimental groups in the case of studied parameters of fattening, bone strength and calcium and magnesium content in the chicken´s liver. Based on the obtained results it could be concluded the reduction of determined elements in the chicken diet did not deteriorate parameters of yield, elements content in liver tissue as well as the bone strength of broiler chickens.