In the course of treating a serious illness, a person is faced with questions related not only to the medical side of treatment, but also with the realizing the sense of the events. This is equally true for both oncology adults and for children.

The paper researches the disease representation in children who suffer from severe diseases. General psychological aspects of the disease situation and the understanding of patient children and the ability to use these concepts in practical psychological help are considered.

The study hypothesizes, first of all, the semantic structure of representation in this group of children having specific characteristics that distinguish them from healthy children. Secondly, data representation having a therapeutic potential can be used as a psychological tool. Mediating function of the psychological tools mentioned is justified in this paper from the perspective of cultural historical approach and the concept of mental health levels. The experimental study was conducted in the specialized pediatric clinics in Moscow, Russia. Control group include students of one of Moscow schools. The study included organization of the experimental situation, criteria for obtaining data, comparative analysis and evaluation.

The hypothesis is confirmed. The characteristic structure of disease representations in patient children reflecting some vector of the disease course is outlined. This makes the study an important practical value as the results may provide a solution to practical issues of medical psychology in assisting patient children. The research offers further studying the semantic sphere of patient children.