The levels of magnesium, zinc and copper in blood serum and in hair in 50 children with hyperactivity were measured. There was also done the assessement of dificiency of these trace elements. There are deficiency of magnesium, zinc and copper both in serum and in hair examinated children. The clinical symptoms of magnesium shortage are observed in both of groups, too. In this connection there seems to be useful, apart from the traditional treatment, to do the magnesium supplementation in children with environmental adaptation difficulties.