Optimisation in X-ray and Molecular Imaging 2020 will cover a wide area of research related to optimisation of medical imaging and is intended for a broad audience of medical physicists, radiologists, nuclear medicine physicians, engineers, radiographers and biomedical scientists, as well as representatives for authorities and manufacturers. The conference is the 5th in a series of scientific conferences focusing on optimisation of medical imaging, with special emphasis on image quality evaluation and radiological protection. Previous conferences have been held in Malmö, Sweden (1999, 2004, 2009) and Gothenburg (2015).