Rat and human MSCs were labeled with maghemite nanoparticles coated with poly-L-lysine, D-mannose-, or poly-dimethylacrylamide. As a control we used either the commercial contrast agent Endorem or uncoated gama-Fe2O3. The best results were achieved with the PLL coating: 70–80% of cells were labelled. Coated maghemite nanoparticles can be used for tracking grafted cells as well as monitoring their migration, proliferation and differentiation in a host organism.