In Children, the process that occurs during a disease its treatment and hospitalization raise many emotions such as fear, helplessness, suffering, frustration, anxiety and distress. Specifically, children undergoing bone marrow transplant experience physical discomfort not only due to the aggressive nature of the treatment but also the imminent risk of death. This study aims to investigate the implications involved in the childs sickness from a psychoanalytical and health psychology point of view as illustrated by clinical vignettes and narratives of sick children who have undergone or will undergo bone marrow transplantation. Children were interviewed during hospitalization and also outpatients. No script of any type was used during the interview, so we focused on the spontaneous responses of children that occurred during the psychological or informal conversations with the health team. Throughout this thesis it was found that the fragile ego and psychic suffering are part of the process of infant illness, and that the children s responses are laden with emotional intensity. It was found that although the child is fragile, many of them can overcome the adversities and pain that the disease and treatment impose on their lives. Through this study we find indications that the child has an understanding of the seriousness of the disease, its treatment and worsening clinical status based on the recognition of the changes occurring in his life and symptoms that are present in his body.