It is known since the beginning of the 20th century that ionizing radiation has an effect on the immune system. The abscopal effect was well known but extremely rare. However, many study groups performed intensive preclinical research in the field. One of the most prominent recent developments of medical science is the introduction of modern immunotherapy to the treatment of cancer. The widespread use of immunotherapy drew again the attention to the possible role of radiation in conjunction with immunotherapy. There is growing evidence that ionizing radiation may potentiate the effect of immunotherapy. Prospective trials have been launched and the results are very much awaited. But research is booming and new targets of immunotherapy are identified, while we have insufficient knowledge about the underlying biological mechanisms. Therefore, it is highly important that intensive basic and translation research be done and its results should provide sound knowledge to design new clinical trials which, we believe, will lead to better treatment of our patients. In this short review we try to give a snapshot about the current state of the combined clinical use of radiation and immunotherapy.