Cancers diagnosed in children below the age of 15 years represent 1.2% of all cancer cases, and survival after a childhood cancer has greatly improved over the past 40 years in all high income countries. This study aims to estimate the number of people living in Italy after a childhood cancer for all cancers combined and for a selection of cancer types. We computed 15-year prevalence using data from 15 Italian population-based cancer registries (covering 19% of Italian population) and estimated complete prevalence for Italy by using the CHILDPREV method, implemented in the COMPREV software. A total of 44,135 persons were alive at January 1st, 2010 after a cancer diagnosed during childhood. This number corresponds to a proportion of 73 per 100,000 Italians and to about 2% of all prevalent cases. Among them, 54% were males and 64% had survived after being diagnosed before 1995, the start of the observation period. A quarter of all childhood prevalent cases were diagnosed with brain and central nervous system tumors, a quarter with acute lymphoid leukemia, and 7% with Hodgkin lymphoma. Nearly a quarter of prevalent patients were aged 40 years and older. Information about the number of people living after a childhood cancer in Italy by cancer type and their specific health care needs may be helpful to health-care planners and clinicians in the development of guidelines aimed to reduce the burden of late effect of treatments during childhood.