The introduction of state-of-the-art tube, detector, and image reconstruction techniques has made ultra-low-dose CT (ULD-CT) of the lungs technologically feasible, resulting in radiation exposure comparable to that of chest X-rays. Due to its high-contrast structures, the lung as target organ is generally well suited for reducing radiation exposure while maintaining diagnostic accuracy, which could already be shown for the earlier development of low-dose CT (LDCT). The current state of the literature already demonstrates significant benefits of ULD-CT for the diagnosis of respiratory diseases, including COPD, pneumonia, interstitial lung disease, pediatric lung disease, as well as in interventional procedures. It is expected that ULD-CT will significantly expand the range of indications for CT and, in certain areas, will be able to replace chest X-rays as the initial imaging modality once its availability in institutions increases. Limitations currently arise from the known dependencies of quantitative methods on radiation exposure and image noise, and the fact that in-depth validation has not yet taken place.