Subacute combined degeneration (SCD) of the spinal cord is a neurological complication arising from vitamin B12 deficiency. Typical findings are demyelination and axonal loss of the posterior and lateral columns of the thoracic and cervical spinal cord, leading to sensory ataxia and paresthesia. Clinical and neurological features and MRI findings all contribute to the diagnosis of this entity. In the Korean medical literature, only one case of SCD involving pre-treatment MRI has been reported. We describe one case of SCD in a post-gastrecto-my patient who initially presented with progressive sensory abnormality in both upper and lower extremities and showed T2 hyperintensity in the posterior and lateral columns of the spinal cord; this diminished, with clinical improvement, after vitamin B12 therapy. Our report includes the MR images obtained during follow up.