Semiconducting polymer nanoparticles (SPNs) are a very promising class of fluorescent nanoparticles that exhibit many advantageous optical and biological properties. However, their potential for optical imaging in clinical applications is currently restricted by limited tissue
penetration. Multimodal SPN-based contrast agents that integrate several imaging modalities into one platform are able to yield a wealth of information through the use of different imaging mechanisms. The inclusion of magnetic resonance imaging (MRI), with its good spatial resolution and deep tissue penetration, enables SPNs to combine the complementary advantages of MRI and optical imaging. This short review explores the approaches adopted in the literature in the nascent field of multimodal optical-MRI SPN-based probes.