Primary tumour and its metastasis with associated secondary paraneoplastic syndromes along with treatment complications of reactions to chemo-radiotherapy constitute common causative factors for various oncological emergencies with imaging playing an important role for early detection as well as for guiding therapy. This chapter will focus on paediatric oncological emergencies which are mostly encountered in the emergency department (ED). While major portion of oncological emergencies are due to long-standing primary cancers with only a few patients presenting with such emergencies having a previously unknown primary tumour. Every radiologist must be having a thorough knowledge of such acute emergencies in the paediatric population in which early diagnosis and management is lifesaving as due to the different biological nature of paediatric malignancies vs adult malignancies.