BACKGROUND: When a doctor diagnoses a child’s illness as cancer, parents very often react by creating wrong and unrealistic theories about the origins of their child’s illness which in turn generates self-blame in the parents, who take responsibility for the disease. OBJECTIVE: To find what are the parents’ beliefs about the origins of their children’s illness. DESIGN: Descriptive study. SAMPLE: Seventy-two couples of parents whose children with cancer are under treatment in the haemato-oncology paediatric ward of the Padova hospital. They have been collected by a no probabilistic method of sampling. METHODS: A questionnaire was used, based on current literature, which investigates the beliefs of the parents as to what are the causes of illness, whether the parents research information about the illness and the origins of cancer and what are the information sources they use in order to establish if there is a connection between these factors. RESULTS: Eighty-seven percent of the sample group thinks that there is a specific origin of their child’s illness: 27% believes the cause is environmental pollution, 26% believes it is due to radiation emissions, 26% believes it is due to genetic factors and 8% believes it is due to other causes. Eighty six percent and 70% of the sample search for information about the illness and its causes; 64% of the parents state that the first meeting with the medical staff, in which the illness is explained and they are informed that there are no known causes that produce it, does not clarify their doubts. The sources more often used to search for more information and explanations are the physicians in the ward, internet and medical books. CONCLUSIONS: This survey confirms the importance of an "advocacy" role of the nurse in educating the caregiver and the need to create instruments which guide the parents in the informative process and the research for good information. Nurses need to be cognizant that their care is crucial not just for the child, but for the entire family.