Neoplastic transformation is associated with alterations of the ion transports across plasma and intracellular membranes. These alterations are crucial elements of the phenotypical reprogramming of the transformed cells and may promote adaptation to hypoxia, malignant progression, tumor spreading and metastasis, as well as therapy resistance. The present review article focuses on ion transport processes in tumor cells that are induced by ionizing radiation and that contribute to radioresistance and therapy failure. In particular, this article introduces radiogenic ion transports across plasma and mitochondrial membranes and discusses their functional significance for cell cycle control, DNA repair, accelerated repopulation, cell migration and metastasis, metabolic reprogramming, adaptation to hypoxia, and radiogenic formation of reactive oxygen species.