In the contrastive year seasons (the polar day, polar night), there has been carried out a study of the external respiration function in teen-agers (40 youths, 39 girls) living in Murmansk. Increased intensity of work of the apparatus of external respiration in the period of the polar night has been detected, in comparison with the polar day period both in the youths and the girls. Effectiveness of alveolar ventilation has been decreased, and respiration spare capacities have been reduced, especially in the girls.