The objective of the study was to evaluate the content of vitamin D in the diet and in blood serum of adolescent girls and the impact thereof on the forearm bone mineral density. Fifty eight girls aged 12-13 years from Warsaw have been examined. Data regarding the intake of vitamin D have been obtained during three 24-h recalls undertaken in one year. The concentration of vitamin D in blood serum has been determined three times in the perspective of one year. Two measurements have been taken in winter, one in the summer. The forearm bone mineral density (BMD) in the non-dominating arm has been examined using p-DXA osteoplan in the middistal and ultradistal section. The diets of the girls examined are characterised by a very low content of vitamin D. The percentage of that content against recommended norm has remained at the level of 20-25%. In both winter periods the sufficient level of vitamin D in blood serum has been observed only among 8.9% of the girls. In the middistal section in the group of non-menstruating girls BMD have been significantly higher, when the level of vitamin D in blood serum exceeded 50 nmol/L.