Imaging a new mass lesion in a child requires careful consideration of a variety of issues. The age of the child is an important factor in determining the appropriate test to start with and the age also helps provide an appropriate differential diagnosis, which can then be used to guide further imaging. The long-term outcome for most children with cancer is very good, with over 70% achieving 5-year survival and presumed cure. Consequently their imaging requirements should be regarded as equal to all other children. Minimizing exposure to ionizing radiation, particularly where follow-up imaging is required is an important consideration. This article focuses specifically on general paediatric radiology and neuro-oncology imaging is not addressed. The pitfalls to be aware of in plain radiography, ultrasonography, computed tomography, magnetic resonance imaging and nuclear medicine (positron emission tomography-computed tomography and single photon emission computed tomography) in children with a proven or suspected malignancy are discussed.