This chapter discusses the types of radiation exposure anticipated, the principles involved in minimising such doses, and the legal frameworks that operate to ensure the aspects that protect the patient. Accounting for such doses into planning and imaging protocols is important so that the magnitude of the extra concomitant dose delivered is understood and minimised whilst still gaining benefit from the on-treatment imaging procedure. Both measuring and modelling the concomitant dose from on-treatment imaging is an active area of research; reducing the dose whilst still maintaining image quality is a key aspect for the patient and service as a whole. On-treatment geometric verification has a different objective to diagnostic imaging and, therefore, dose considerations should ensure geometric positioning of the high dose volume for treatment rather than diagnosis. Individual image quality is highly dependent on dose and upon the modality and technology involved.