The receptor of vitamin D (VDR) is present in most non-skeletal human cells, suggesting its role beyond the bone and calcium metabolism. The relationship between vitamin D and the respiratory tract is a consequence of its activity in the immune system. Some gastrointestinal diseases, such as inflammatory bowel disease, coeliac disease, liver, pancreas or cardiac diseases, lead to vitamin D deficiency. Many studies indicate a correlation between vitamin D and diabetes. VDR and 1α-hydroxylase have been detected in the cutaneous capillary vessels, endothelium, vascular smooth muscles, myocytes and cardiac fibroblasts. The influence of vitamin D on the expression of genes related to the vascular walls implies its role in the pathomechanisms of vascular diseases and the cardiovascular system. Due to the VDR detected in most immunocompetent cells, calcitriol can modulate the congenital and acquired immune system. The correlation between vitamin D and cancer development is also not surprising because of many functions which vitamin D has in the organism. The vitamin D-regulated genes encode the proteins which participate in differentiation, proliferation or apoptosis. This paper aims to focus on the less well known roles of vitamin D in the organism, especially considering that most "sun consumers" know only its antirachitic and bone reinforcing action. So, this article may be surprising, and first of all it should convince everyone to vitamin D supplemention.