Nutritional status is an important factor in treating a child with malignant diseases. It represents the totality of the successful therapeutic process in order to reduce tumor disease, the application of adequate supportive procedures, and then the cure. Preservation of an adequate nutritional status contributes to a complete immune response and thus to the reduced ability to develop hospital infections to determine the connection between the malnutrition and hospital infections. In this retrospective study, the nutritional status data of a single child were analyzed with a parallel representation of microbiological and bacteriological surveillance of infectious conditions. The variables used to evaluate the nutritional status were: weight, height, body mass index, and childhood-specific centile age curves. The research was conducted in the Pediatric Solid Tumor Reference Center of the Ministry of Health of the Republic of Croatia for 12 months of 2016 with the permission of the Ethics Committee of the Children's Hospital Zagreb. The conducted research shows that about 46% of children with malignant illness at some stage of treatment have faced malnutrition. Based on data analysis, we can talk about the relationship between the disrupted nutritional status and the appearance of hospital infections. The study found that 32.4% of children with hospital infection were also malnourished. This figure suggests that malnutrition is not critical to the occurrence of hospital infection, but it is a serious threat and should not be ignored in treatment protocols.