Hyponatremia and its rapid correction may cause osmotic demyelination syndrome (ODS) with damage to the pontine and extrapontine areas of the brain. The damage may become persistent or may regress and disappear during follow-up. We describe the case of a 35-year-old woman with chronic renal failure who was admitted to the emergency department with profound hyponatremia which was corrected rapidly after hemodialysis treatment. During follow-up, she developed quadriparesis and dysartria. Magnetic resonance imaging (MRI) demonstrated abnormalities characteristic of ODS in the pons as well as the basal ganglia with increased signal intensity on T2 and diffusion-weighted (DW) MRI and low apparent diffusion coefficient (ADC) values. After the sixth day, her clinical status improved progressively. Control MRI revealed rapid normalization of the ADC values during the first week and month parallel to the clinical improvement. However, the hyperintensities on T2-weighted images persisted. Four months later the MRI findings were completely normal. The close relationship between the ADC abnormality and the clinical status suggests that DW-MRI may be useful in predicting the prognosis of ODS.