BACKGROUND: Vitamin D deficiency in secondary hyperparathyroidism (SHPT) against the background of chronic kidney disease (CKD) in patients with diabetes mellitus (DM) is one of the key factors in the deterioration of renal function. AIM. To assess the indicators of calcium-phosphorus metabolism in individuals with SHPT against the background of CKD, diabetes and without it to optimize treatment approaches. MATERIALS AND METHODS. A retrospective analysis of 416 medical records with diagnoses CKD3-C5 and SHPT was carried out, of which 112 had a history of diabetes, which were examined and treated in the nephrology department of the in the period from 01. 01. 2018 to 31. 12. 2022. Demographic and anthropometric data were studied, laboratory (total and ionized calcium, total protein, albumin, phosphorus, creatinine, parathyroid hormone, 25(OH)D, alkaline phosphatase) and instrumental (ECHO-CG, ultrasound of the abdominal organs and retroperitoneal space) research methods. RESULTS. Diabetes is the leading cause of CKD among all nosological forms. The level of 25(OH)D in patients without diabetes varied from 9.04 to 152 nmol/l, with diabetes from 8.3 to 77 nmol/l. The average level of 25(OH)D in patients without diabetes (41.7 ± 26.1 nmol/l) was significantly higher than in patients with type 1 diabetes (20.3 ± 14.9 nmol/l) and type 2 diabetes (27.6 ± 19.2 nmol/l) (p = 0.005 and p = 0.003, respectively). 25(OH)D deficiency and insufficiency were more often recorded in patients with diabetes compared with patients without carbohydrate disorders (89 % and 10 % versus 69 % and 19 % respectively), while the optimal level was more common in patients without diabetes (12 % and 1 %, respectively).