Children’s hospitalization is a complex condition which needs psychological intervention to promote patient’s better behavior, facilitating their adaptation. Experimental and observational procedures were proposed to describe and assess an assistantship program for hospitalized children during an inhalation medical procedure, observing the decrease of concurrent behavior (responses which can cause difficulties, delays or impediments to the medical procedure) and the increase of adequate behavior (responses which facilitate the medical procedure). The Observational Scale of Distress Behavior (OSDB) was used to define and the register the infant behavior categories. This research was carried out with 20 children distributed in an experimental group (N= 10) and a control group (N= 10). Children from the experimental group followed the Activities Program, which included the development of infant reading related strategies, simulations, relaxation techniques and fantasy. The data analysis demonstrated that the experimental group showed a more adequate behavior pattern contributing to the inhalation medical procedure (a decrease in concurrent behavior and an increase in acceptance behavior). Furthermore, the functional relationships in the hospital environment were better understood and consequently improved patient behavior. Results from this study will support the development of psychological programs for medical procedures in hospitals.