<p>Electromagnetic (EM) radio-wave technologies for medical imaging represent an emerging alternative diagnostic modality with some unique features, which is attracting the attention of many researchers worldwide. Diagnostic devices based on EM technology have no side-effects, as they exploit non-ionizing radiation, and their intrinsic low cost makes them sustainable for healthcare systems. This Special Issue provides a comprehensive account of this very active research area by gathering contributions that cover a variety of topics ranging from fundamental research questions to experimental validation and clinical translation.</p>