The aim of this investigation is to evaluate the accuracy of the diagnostic parameters of the radiological features, especially in conventional lumbar myelography, since these will be used in the future as a gold standard for new developing diagnostic methods like ultrasonography (US) and magnetic resonance imaging (MRI). A short review of the clinical symptoms and diagnostic radiology of the tethered spinal cord (TSC) is given. The radiological features of the TSC syndrome are compared with the peroperative findings in 30 patients investigated and operated in our hospital. All patients showed lumbar or sacral osseous malformations on the plain X-ray films. This means a high diagnostic sensitivity although the specificity for TSC is low. Conventional myelography had a sensitivity of 0.82 and positive predictive value of 0.94, while the specificity and negative predictive value are respectively 0.96 and 0.85. The positive predictive value of the total diagnostic procedure of plain X-ray films and lumbar myelography for TSC may be estimated at 1.