Diagnostic imaging is pivotal in the initial detection, characterization, staging and post-treatment follow-up of patients with high-grade osteogenic and Ewing's sarcoma. In the present review article, conventional and new imaging modalities are discussed with regard to the monitoring of the effect of neoadjuvant chemotherapy in such patients. Presurgical monitoring of response to chemotherapy may have an impact on modification of neoadjuvant treatment protocols, on patient selection for the performance and timing of limb-salvage surgery and on planning of radiation therapy (in non-operated Ewing's sarcomas) and selection of postoperative chemotherapy regimens. Dynamic contrast-enhanced MR imaging, as part of a routine MR protocol, assists in the detection of the most viable parts of the tumour and serves as an initial standard for follow-up of the metabolic activity of the tumour during and after chemotherapy, both in small intraosseous tumours and in tumours with an associated soft tissue mass. In combination with selected morphological features, dynamic imaging parameters are therefore advocated for monitoring the effect of neoadjuvant chemotherapy in patients with osteogenic and Ewing's sarcoma.