A 35 years old female patient was admitted to our neuro-pain clinic with symptoms of low back pain(L4, L5 level) radiated to both lower(L3, L4, L5 level) extremities that developed 6 years prior to admission. Upon initial physical examination, motor weakness or sensory deficit was absent. But on straight leg raising test, it was restricted to 60 degree in both lower extremities. Low back pain and radiating pain improved significantly after we performed epidural steroid injection. However on the next day of procedure the patient complaints more pain and started to experience severe pain during overnight for 3 days. On computer tomography(CT, L3-S1 level), we find suspicious lesion of herniated nucleus pulposus at L5-S1. Otherwise were within normal limits. Based on these symptoms, to find the other lesions, subsequently magnetic resonance imaging(MRI) was performed. Spinal tumor was seen at L2-3 level(2 2 4 cm). Neurosurgical surgery was recommended, and operation was performed. The patient was diagnosed to ependymoma after excision and cytologic studies. Even if one lesion was diagnosed, it must be put off until any other diseases or underlying cancer are ruled out. We report a patient with spinal cord tumor missed on CT, but revealed on MRI in the evaluation and management of herniated nucleus pulposus related(L5-S1) low back pain.