Objective: The use of proton beam therapy (PBT) increases in the treatment of some cancers, especially in the critical organs. Contrary to traditional radiotherapy, protons limit the radiation of healthy tissues. Due to high cost of treatment and limited options, decisions to treat adults with PBT must be based on relative value compared to the current standard of care. The purpose of this publication is to assess the budgetary impact of using PBT in 8 selected oncology indications in Poland. Methods: The budget impact analysis (BIA) was carried out in a 3-year time horizon. The ‘new’ scenario presents the estimated costs of PBT in adult population while the ‘existing’ scenario includes only other forms of radiotherapy – IMRT and stereotactic radiotherapy. Cost data reflect the estimated costs incurred by the public payer (NHF) in providing health benefits. Sources of data were: epidemiological data, opinions of clinical experts, scientific evidence and NHF data. Results: Total incremental cost of the base case with PBT was about €34.6 million (€10.4 million, €11.5 million. and €12.7 million in each year of analysis). In comparison to ‘existing’ scenario cost increased approximately 2.75 times (total costs from €19.8 million to €54.4 million, cost per patient from €5,543 to €15,265). Sensitivity analysis revealed that total incremental costs in the minimum scenario were over 20% lower than in base case, while the cost in maximum scenario was similar to base case. Conclusion: The expected costs of PBT in adult cancer patients in Poland significantly exceed the costs of treatment with IMRT and stereotactic radiotherapy. Keywords: proton beam therapy, PBT, budget impact analysis, BIA, economic analysis, pharmacoeconomic analysis