The knowledge of the epidemiology of cancer in childhood is relevant of a strict methodology allowed by the activation of population-based specific registries, case-control and cohort studies. Descriptive epidemiology is a mean of survey and of public health, while analytic epidemiology contributes to define the role of genetic and environmental factors, along with their interaction. The collected data help indirectly to improve the care of the child with cancer and to a better understanding of the carcinogenesis.