The CT is an important and valuable instrument in the study of the postoperative lumbar spine, in the patients which presented persistent clinical manifestation. In this report the technique with contrast enhancement is outlined, the criteria for its interpretations are presented, and its advantages and limitations are reviewed; pitfalls in technique interpretation are stressed. Two hundred and fifty patients are referred to the CT without and with i.v. contrast medium for this diagnostic request: scar or herniation at surgery level.