Anorexia nervosa (AN) most often has its onset in adolescence, which is a crucial period to achieve peak bone mass. The hormonal abnormalities (hypoestrogenism, hypercortisolism, decreased secretion of dehydroepiandrosterone, testosterone, insulin-like growth factor) and malnutrition are associated with profound bone mineralization disorders. Densitomertic bone mineral density (BMD) values for osteopenia and osteoporosis were found respectively in 35–98% and 13–50% of women with AN. Prospective studies indicate a further decline in BMD at the beginning of treatment and a crucial importance of weight gain and return of spontaneous menses for its growth. Due to frequent chronic and relapsing course of AN densitometric assessment of BMD is recommended in all patients with AN and amenorrhea lasting around twelve months. In order to establish standards for the treatment of osteoporosis in AN, studies on pharmacological treatment are conducted. There are promising results indicating the improvement in BMD after treatment with physiologic oestrogen replacement treatment and sequential administration of medroxyprogesterone in teenage girls and bisphosphonates in adult women. Supplementation of vitamin D and adequate consumption of calcium from diet are recommended. Further studies on the effectiveness of long-term treatment of osteoporosis with regard to the possibility of increase in BMD and reducing the risk of osteoporotic fractures are needed.