In the experiment, the features of laser interstitial thermotherapy (LITT) with wavelengths of 0.92; 0.97; 1.06; 1.56 and 1.9 μm and the possibility of estimating photothermal interactions by means of ultrasoundwere studied. Ultrasound clearly determined the tissue coagulation zone without differentiating it from carbonation. The phenomenon of "breakdown" of tissues during LITT was revealed. Most often at 1.9 Μm-LITT there was a rapid transfer of heat by gas bubbles through the vessels. Intima of the vessels was fired. Ultrasound control of LITT in 145 of 781 children with vascular tumors increased its effectiveness, reducing the number of repeated sessions by 3.2 times.