Despite many difficulties, the field of cardiac dif-fusion imaging is slowly but steadily making progress. In recent years it was demonstrated that reproducible measure-ment of diffusion parameters and fiber architecture in healthy and diseased hearts is possible. In this review we will discuss the basics of diffusion imaging as well as various reconstruc-tion and analysis models. Furthermore, we cover the main challenges and proposed solutions that come with in vivo cardiac diffusion imaging. In vivo and ex vivo diffusion imaging of the heart has shown that the technique has great potential to better understand cardiac function, characterize cardiac pathology, and understand myofiber remodeling in response to injury or disease.