The aim of this prospective triple-blind randomized study was to determine if a free fat transplant used in operation in lumbar disc herniation could reduce the degree of intraspinal scar tissue and to evaluate whether the scar tissue could lead to symptoms. Ninety-nine patients were subsequently examined after median 376 days. The clinical outcome was scored using the Low Back Pain Rating Scale. Enhanced CT-scanning was assessed regarding the degree of scar tissue and survival of the fat transplant. There was no difference in the clinical outcome between the two groups. Significantly fewer had dural scarring in the group who had a free fat transplantation, but there was no difference regarding the degree of radicular scarring. The transplant was shown on CT-scan at the follow-up examination in 66% of the patients who had a fat transplantation. Free fat transplantation can reduce the degree of dural scar tissue after operation for lumbal disc herniation, but does not result in a clinically better outcome.