['This study was designed to evaluate vitamin D status with separate determination of 25-OH D2 and 25-OH D3 and its relationship to vitamin D binding protein (VDBP) in patients with chronic kidney disease (CKD) and long-term haemodialysis patients (HD).', '45 CKD patients, 103 HD patients, and 25 controls (C) were included. Plasma vitamin D concentrations were determined using chromatography and VDBP in serum and urine in CKD using enzyme immunoassay.', 'Plasma vitamin D levels were lower in CKD (30.16\u2009±\u200916.74\u2009ng/mL) and HD (18.85\u2009±\u200915.85\u2009ng/mL) versus C (48.72\u2009±\u200918.35\u2009ng/mL), P < 0.0001. 25-OH D3 was the dominant form of vitamin D. Serum VDBP was higher in CKD (273.2\u2009±\u200993.8\u2009ug/mL) versus C (222\u2009±\u200987.6\u2009ug/mL) and HD (213.8\u2009±\u200970.9\u2009ug/mL), P = 0.0003. Vitamin D/VDBP ratio was the highest in C and the lowest in HD; however, there was no correlation between vitamin D and VDBP. Urinary concentration of VDBP in CKD (0.25\u2009±\u20090.13\u2009ug/mL) correlated with proteinuria (r = 0.43, P = 0.003).'] Is vitamin D Binding Protein Involved in Vitamin D Deficiency in Patients with Chronic Kidney Disease?