Hadron therapy (HT) with protons and carbon ions is an advanced radiotherapy technique. As the first report addressing this topic, the present study aimed to estimate the number of patients eligible for HT in Fars province and the whole of Iran. The data were collected through direct inspection of medical records of the patients treated at the Radiotherapy Department, Namazi Hospital, Shiraz, Iran in 2014. The patients who were treated with external-beam radiotherapy and declared to be a resident of Fars province were extracted from the medical records. After classification based on appropriate indications and factors, the number of eligible patients in Iran was calculated by scaling (Iran: Fars population). Of the 2,932 medical records, 1,943 patients were treated with external-beam radiotherapy, among which 1,536 were from Fars. The total number of patients eligible for HT in Fars was >351 cases/year (22.9% of the treated patients). The cancer site distribution of the eligible Fars residents was central nervous system primary tumors (n=31), brain metastases (n=64), eye (n=7), head and neck (n=28); thyroid (n=4), lung (n=17), breast (n=56), esophagus (n=5); pancreas (n=5), gastric (n=32), liver and bile duct (n=0), rectum and anus (n=26); prostate (n=27), bladder (n=8), cervix (n=6), soft tissue (n=17); kidney (n=1), Hodgkin lymphoma (n=9), non-Hodgkin lymphoma (n=4), and bone metastases (n=4). A total number of 5,756 cases/year was estimated for the entire country. Considering the experiences of other countries, these results suggest that establishing at least two HT centers (covering the northern and southern parts of Iran) is justified based on the total number of patients. Further accurate estimations and cost evaluations are recommended.