Many scientific works, concerning an impact of vitamin D and its active form – 1,25-dihydroxyvitamin D [1,25(OH)2D] on human health, appeared lately. Vitamin D deficiency, defined as low level of 25-hydroxyvitamin D (25(OH)D), is a global health problem. It is generally accepted in Poland, that vitamin D skin synthesis, necessary for maintenance its proper level, can take place between April and September, if the sun skin exposure, without sun blockers, covers 18% of body area for 15 minutes daily. It’s been scientifically proven that commonly used for prevention and treatment vitamin D doses are safe. Toxic concentrations of 25(OH)D is above 200 ng/ml. Recommendations concerning vitamin D supplementation are commonly available for all age groups. Polish recommendations were presented in 2009. Nevertheless there are clinical situations when vitamin D supply is potentially harmful. One of them is urolithiasis, especially when stones are made of calcium. On the other hand, there is relationship between idiopathic hypercalciuria and low bone density. Vitamin D acts, among others, as factor increasing intestinal calcium absorption. Calcium absorbed to the blood builds bone mass, but is excreted with urine as well. Low calcium diet paradoxically favours urolithiasis. Systemic scientific analysis of adult population lead to conclusion that too low and too big calcium supply made conditions conductive to produce renal stones. Not numerous epidemiological analysis did not demonstrate relation between vitamin D supply and the risk of urolithiasis. But in available literature it is difficult to find recommendations concerning supplementation of vitamin D in children with hypercalciuria and renal stones. Proper level of vitamin D has great impact on children’s development and health. It seems that careful vitamin D supply, with the use of calcium blood and urine level and 25(OH)D and alkaline phosphatase activity monitoring, could be of benefit in such patients.