Complications following lumbar spine surgery are reported to occur in 15 to 30% of cases. Acute postsurgical complications (hematoma, infection.) require urgent imaging. Imaging of recurrent pain following lumbar surgery, often with a clinical presentation that is poorly specific in nature, is sometimes difficult. Selection of the initial imaging technique must simplify the diagnostic work-up. Because of its high contrast resolution, pre- and postcontrast MRI is the most effective imaging technique. Noncontrast CT may be added to facilitate detection of bony abnormalities. Diskography with post-diskogram CT can be added as well in patients with discordant results at clinical and imaging work up. The main causes of failed back syndrome are recurrent disk herniation (usually easily diagnosed), postsurgical granulation tissue/epidural fibrosis (diagnosed based on imaging) and central or lateral bony spinal stenosis. Spondylodiskitis, arachnoiditis and pseudomeningocele are other less frequent etiologies.