Résumé : Numerous and diverse contrast agents are available in MRI. Their use is focused on two directions : microcirculation imaging and cell capture imaging. Microcirculation imaging uses gadolinium chelates and technical advances in MRI. It quantifies perfusion and capillary permeability applying a physiological analysis to the tissue enhancement curve. Cellular imaging uses labeled cells as contrast agents ; the cells can be labeled in vitro or in vivo. The roles of imaging in cancer are numerous. For diagnosis, detection is improved, particularly for liver metastases with the development of cellular imaging and liver-specific contrast agents. Cellular imaging opens promising perspectives for cellular therapy. Microcirculation imaging characterizes tumors more specifically, particularly in breast imaging. Regarding treatment follow-up, the impact of imaging is considerable. Microcirculation imaging predicts treatment response even before initiation of therapy. During treatment, it allows a more complete evaluation taking into account physiological parameters, better adapted to monitor therapies currently in development, such as anti-angiogenic drugs. Therapeutic effects can be detected earlier, before morphological changes. Cellular imaging offers new prospects to monitor cellular therapy. The use of MRI contrast agents is moving towards the coupling of functional to morphological analysis. This constitutes a new approach perfectly adapted to diagnosis and therapy follow-up in oncology.