Early hospitalization is a critical experience in a child’s life, with personal and relational effects and repercussions on school learning and achievement. In this paper, we will illustrate the main studies conducted on the psychosocial impact of hospitalization on school-children’s well-being, with a specific focus on surgical intervention, as a particularly invasive medical procedure. We will then present an explanatory research to investigate the mathematical abilities of a group of children with a recent history of hospitalization, who has undergone at least one surgical operation, at the beginning of primary school. Finally, we will compare their mathematical competence with that of a control group of the same age and schooling.