Background/Aim. Anemia is a common complication in hemodialysis patients. Treatment of anemia is affected by iron deficiency, insufficient dose of erythropoietin, microinflammation, vitamin D deficiency, increased intact parathyroid hormone concentration and inadequate hemodialysis. The aim of the study was to determine the prevalence of vitamin D deficiency and its impact on hemoglobin con-centration, iron status, microinflammation, malnutrition, dialysis adequacy and erythropoietin dose in patients on regular hemodialysis. Methods. The study involved 120 patients divided into three groups: severely deficient of vitamin D: 25- hydroxyvitamin D[25(OH)D] < 10 ng/mL; deficient ? 25(OH)D within range of 10?20 ng/mL, and insufficient ? 25(OH)D > 20 ng/mL. For statistical analysis Kolmogorov- Smirnov test, the single-factor parametric analysis of variance ? ANOVA and Kruskal-Wallis test were used. Results. The prevalence of vitamin D deficiency in patients on regular hemodialysis was 75.83%, while the prevalence of severe vitamin D deficiency was 24.7%. Patients with severe vitamin D deficiency had lower blood concentration of hemoglobin, hematocrit, serum concentration of total proteins and albumin, and dialysis indices were also lower compared to the other two groups of patients. The level of C-reactive protein was significantly higher in the group of patients with severe vitamin D deficiency than in the two rest groups. Conclusion. Hemodialysis patients with severe vitamin D deficiency have lower hemoglobin, lower dialysis adequacy, significant microinflammation, malnutrition, bone metabolism disorders and need higher dose of erythropoietin than patients whose vitamin D was higher than 10 ng/mL. Vitamin D is important risk factor for development of anemia in hemodialysis patients and important factor that can affect treatment of anemia in these patients.