Whole body MRI provides excellent contrast resolution imaging and is an interesting alternative to nuclear medicine examinations in paediatric oncology because it does not involve exposure to radiation. This technique, now feasible in clinical practice, helps to evaluate metastatic spread and response to treatment, which are of great prognostic interest. Numerous studies have demonstrated the non-inferiority of this technique when compared to nuclear medicine examinations. However, there is still a need to standardize indications in each type of cancer and at every stage of it. This article first discusses the technical principles of whole body MRI, then reviews current clinical applications for the modality in children, and finally, discusses future useful developments for paediatric oncology.