The optic nerve and spinal cord are technically challenging to investigate with any magnetic resonance imaging (MRI) technique due to the effect of the surrounding cerebrospinal fluid and lipid, and the presence of nearby bony structures. Motion and the relatively small cross-section of the structures make diffusion-weighted imaging even harder. With careful choice of pulse sequence and parameters, however, apparent diffusion coefficient (ADC) measurements are now possible in the optic nerve, and both ADC and diffusion tensor imaging (DTI) measurements are becoming available in the spinal cord.