In the spinal motion segments, the inferior articular processes and the caudad portions of the laminae form, by means of their articulation with the superior articular process of the underlying vertebra, a structural and functional unit. This posterior structures protect the disc from excessive shear loads in axial rotation and guide the relative movement of the spinal segments by the orientation of the planes of these strucrures. There are different opinions about the role of orientation and asymmetry of facet joints whether it causes the herniation of intervertebral disc or not. The authors supposed that asymmetry of facet-lamina angle contribute to the herniation of intervertebral disc much more than the asymmetry of facet joint alone. And we evaluated the orientation of facet joints and laminae in 30 normal persons as a control group and 30 unilateral protrusion of the L4-5 disc and same number of unilateral protrusion of the L5-Sl disc as a study group on coronal computed tomography (CT) scans. Orientation of laminae are more sagittal in L4-5 than L5-S1, but there are no significant differences in orientation of facet joints between L4-5 and L5-Sl. We can't find any significant differences in orientation and asymmetry of facet angle, laminar angle and facet-laminar angle between control and study group, even though there are some tendencies to more sagittal facet and laminar angle and more asymmetric facet-laminar angle in study group. These results indicate that each one of orientation and asymmetry of facet, laminar and facetlaminar angle is not definitely related to the development of heraiation of intervertebral disc.