With trauma being a leading cause of death for children, identifying all sustained injuries remains a priority for clinicians, and imaging is a key diagnostic tool to ensure that is achieved. However, children have a greater risk of detrimental effects of ionising radiation than adults. Clinicians therefore have to balance limiting their patients’ radiation exposure to ‘as low as reasonably achievable’ with the need for diagnostic accuracy. But what is ‘reasonable’ in major trauma can be confusing. This article aims to clarify the current guidance on which body part to scan and when in paediatric major trauma.