Thoracic imaging plays a major role in the non-invasive approach to the diagnosis and management of thoracic disease. Techniques that use ionizing radiation (radiography, computed tomography, nuclear medicine) are the most useful approaches for imaging the thorax. Both the availability and the clinical indications of these imaging procedures are growing rapidly, which means that the radiation dose that patients may receive is increasing. The goal of this paper is to review briefly the factors that determine the radiation dose, to highlight the risks associated with radiation exposure, and to describe the techniques that can be used to reduce the radiation dose that patients with respiratory disease are exposed to.