The aim of the study was to determine the relationship between the serum selenium concentration (Se–S) and the blood concentrations of osteoprotegerin (OPG), receptor activator of nuclear factor kappa-Β ligand (RANKL) and the OPG/RANKL ratio in patients with arterial hypertension. The study group comprised 138 patients with arterial hypertension (age: 56.04 ± 11.59 years). Se–S was determined in all the subjects. Based on the Se–S, the following subgroups were distinguished: a subgroup of patients with a lower Se–S ("low-Se", Se–S < median) and a subgroup of patients with a higher Se–S ("high-Se", Se–S ≥ median). Moreover, the blood concentrations of the parameters of bone metabolism and extraskeletal calcification were assessed: OPG and RANKL. The OPG/RANKL ratio was calculated. In the "low-Se" subgroup, the RANKL concentration was statistically significantly lower, and the OPG/RANKL ratio was statistically significantly higher than in the patients in the "high-Se" subgroup. The correlation analysis showed the negative linear relationships between Se–S and OPG (r = − 0.25, p < 0.05) and between Se–S and OPG/RANKL (r = − 0.47, p < 0.05). Moreover, Se–S positively correlated with RANKL (r = 0.33, p < 0.05). In regression analysis, higher body mass index (BMI), smoking and lower Se–S were independently associated with a higher OPG/RANKL ratio, while lower BMI, use of diuretics, β-blockers and ACE inhibitors and lower OPG/RANKL ratio with effective blood pressure control. In summary, in the group of patients with arterial hypertension, lower Se–S is associated with an unfavourable prognostic panel of parameters of bone metabolism and extraskeletal calcification. Lower Se–S is an independent risk factor for a higher OPG/RANKL ratio, which is an independent prediction factor of ineffective blood pressure control in patients with hypertension.