BACKGROUND: Though vitamin D deficiency is a global problem with wide spectrum of severe public health consequences, inadequate vitamin D status still remains one of the most common and untreated medical conditions. Thyroid diseases, including hypothyroidism, also represent the most frequent endocrinopathies in general population. OBJECTIVES: To determine the vitamin D status in hypothyroid patients and to ascertain the status of thyroid hormone replacement. METHODS: The 25(OH)D concentrations (ECLIA) in 71 hypothyroid patients recruited in the Outpatient Clinic of Endocrinology or Department of Clinical Endocrinology were assessed. The examined group was composed of 59 subjects diagnosed with primary hypothyroidism of different etiology and 12 patients with secondary hypothyroidism. The control group included 16 healthy individuals. RESULTS: Mean serum 25(OH)D concentration in healthy volunteers was significantly lower than in hypothyroid subjects (13.09±1.63 vs. 19.92±1.37 ng/mL). Patients with a history of thyroidectomy presented with significantly higher mean 25(OH)D concentration than controls (23.25±2.75 vs. 13.09±1.63 ng/mL). Mean serum 25(OH)D concentration in effectively treated hypothyroidism was significantly higher than in controls (21.90±1.47 vs. 13.09±1.63 ng/mL) or undertreated hypothyroidism (21.90±1.47 vs. 13.52±3.39 ng/mL). Hypothyroid patients aged under 60 years presented with significantly lower mean 25(OH)D concentration than elders (16.46±1.54 vs. 24.39±1.18 ng/mL). The major 25(OH)D deficient (≤10 ng/mL) or deficient (≤20 ng/mL) hypothyroid patients were significantly younger than those with 25(OH)D concentrations exceeding 10 ng/mL or 20 ng/mL respectively. CONCLUSIONS: These findings confirm the necessity for vitamin D status improvement in the general population and more effective healthcare of hypothyroid patients.