Аннотация:It is shown that, in the case of T Tau type stars, the He II 4686 line is optically thin and can be used to obtain information about the nature of the hot (T not less than 30,000 K) regions. Profiles of this line are calculated for three hot-region models: the chromosphere, the accretion disk, and the chromosphere above the disk. A choice between these models can be made by studying the profiles of the He II 4686 line from spectrograms with a resolution of about 20 km/s.