Purpose: The present study examines the differences of radiological diagnosis of lumbar prolaps with quantitative and morphological criteria. Advantages and disadvantages of both methods were analysed. Method: Concerning the "Deutsche Wirbelsäulenstudie" (DWS) 286 male and 278 female patients between 25 and 70 years of age undergoing clinical or ambulant therapy for radicular symptoms and the diagnosis of a lumbar prolaps in CT and/or MRT were integrated into our study. Actual MRT and CT pictures of the patients' lumbar spine were analysed by an independent radiologist (primary radiologist). Radiological diagnosis was concerned with quantitative and morphological criteria. Radiological images of 100 selected patients were reexamined by another radiologist (secondary radiologist). On the basis of these results, the interobserver reliability (kappa) was calculated. Results: In 95.2% of all segments a prolaps was seen with quantitative and morphological criteria, in 4.5% a prolaps was analysed with quantitative and in 0.3 % a prolaps was seen with morphological criteria. The radiological diagnosis of prolaps by quantitative criteria was confirmed by the operative findings. Many prolapses with lateral localisation were seen in these cases. Therefore radiological diagnosis on the basis of morphological criteria could be difficult. For both radiological methods similar interobserver reliabilities were calculated. To sum up both radiological methods are even equivalent. It is also possible to graduate the diagnosis with quantitative criteria. Detrimental effects of quantitative criteria could be difficulties in measurement with non-digital images. Conclusion: Besides several recommendations in the international literature on the radiological analysis of prolaps with morphological criteria, diagnosis with quantitative criteria is also an effective method.