Published in the Green Journal, this report aimed to establish treatment indications and potential patient numbers for carbon ion radiation therapy (CIRT) at the proposed national carbon ion (and proton) therapy facility in the Westmead precinct, New South Wales, Australia. The greatest level of consensus was reached that CIRT in Australia can be justified currently for patients with adenoid cystic carcinomas and mucosal melanomas of the head and neck, hepatocellular cancer and liver metastases, base of skull meningiomas, chordomas and chondrosarcomas. A conservative estimate is that 1% of cancer patients in Australia (or 2% of patients recommended for radiation therapy) may benefit from CIRT for initial therapy of radiation resistant tumors, or to boost persistently active disease after other therapies, or for re-irradiation of recurrent disease. Almost 1400 Australian patients annually meet the consensus-derived indications now. With capacity to treat around 250 patients with CIRT per treatment room, a single national facility with up to four carbon ion treatment rooms is justified.