These investigations are devoted to the problem of medical consequences of Chernobyl catastrophe to the children`s population of Ukraine. Concerning different reports, Chernobyl accident negatively influenced to the children health indexes. Astonishing fact is that among children under radiation action only 2,1% have no functional deflexions (I group of health) and 28% have chronical diseases with frequent aggravation. Our previous investigation in children evacuated from 30 km zone showed unfavourable changes in immune system. We have shown the data of investigation carried out in the frames of National Program ``Children of Chernobyl``. We have studied the morbidity, some immune functional characteristics and metabolism indexes in 2700 children aged 0-15 years, continually living within radiation contaminated territories. The results were compared with the control indexes, obtained during examination of 980 children from relatively ``clean`` regions. 15 refs, 5 figs, 1 tab.