In radiotherapy, the use of proton beams is one of the most promising approaches in order to reduce the treatment volume and, consequently, increase the total dose avoiding severe complications to the normal tissues surrounding the target. Among the new hospital-based facilities that are planned for the next future, the italian project is in an advanced stage of study. Because of the complexity and high cost of the italian centre, one of the most important information in order to establish the cost/benefit balance, is represented by the number of potential patients to be treated for the various pathologies. For this reason it is useful to define a priority scale of clinical indications and, on this basis, to estimate the yearly patient afflux to the center, taking into account the incidence and the expected new cases to be treated with protons. Indications have been divided into two categories, according to decreasing priority. Category A includes all the tumors in which the use of proton therapy has clearly demonstrated to be advantageous, being the only way to give a curative dose to the target. In Italy, the estimated number of this category of patients is 825 each year. Category B comprises a great variety of tumors characterized mainly by a local evolution, with a limited likelihood of distant spread, and therefore potentially cured if the local control can be obtained. The total number of potential patients in this category is more than 10,000.