Cancer therapy increasingly relies on custom treatment according to individual patient needs. Polymeric carriers offer the greatest potential in customized therapy due to their large diversity and the possibility to introduce various functionalities like chemotherapeutics and targeting moieties. Nuclear medical imaging techniques such as Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) play an indispensable role in the evaluation of their in vivo characteristics. In order to use these techniques effectively, efficient radiolabeling of these carriers with good in vivo stability and minimal influence on their native behaviour is essential. This review provides an overview of the different methods to radiolabel the polymeric carriers and their application in nuclear medicine - mainly to image the in vivo behaviour of the carriers, though some are developed as radio-therapeutics.