This chapter focuses on the main findings and advances brought by magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) to the understanding of prodromal and early-stage patients. In Huntington's disease (HD), as in many neurodegenerative disorders, accurate markers of disease progression that reflect pathogenic mechanisms are currently lacking, and therefore are an important focus of current research. MR techniques are a particularly promising tool in the identification of such biomarkers. Using MRI, cerebral blood flow (CBF) or perfusion can be quantitatively measured using a technique named arterial spin labeling (ASL). For measuring brain activity, another technique can be used, namely blood oxygen level-dependent (BOLD) imaging. MRI is based on the detection of the proton signal within water molecules. Finally, the chapter reviews new approaches used in animal models that will hopefully be translated in clinical studies in the near future.