Radiotherapy remains a cornerstone of oncological treatment modalities for many types of tumors. Recently, preliminary studies have evidenced that ionizing radiations delivered by High Tech Linear Accelerators may increase the effectiveness of patients' antitumor immunoresponse in the clinical setting even at distant sites. Radiations may awake the dormant antitumor T-cells by promoting also an "abscopal effect", i.e. the control of metastasis outside the irradiated tumor site. These emerging findings have stimulated the design of combinations of high tech radiotherapy with new immunotherapies in order to obtain a synergy against biologically aggressive cancers. In preclinical model and clinical trials radiotherapy has been widely associated with citokines, peptides, immunoagonists and mainly with immune checkpoint inhibitors to counteract the function of CTLA-4 or Programmed-Death-1 receptors or PD-L1/L2 ligands. In this review the complex biological processes induced by radiotherapy on immunosystem are briefly explained. Although several trials are still ongoing, the preliminary interesting results obtained by this innovative radio-immunotherapy synergy to control advanced malignancies are reported and discussed.