Objective : Bilateral laminotomy and unilateral laminotomy for bilateral decompression are becoming the minimally invasive procedures for lumbar spinal stenosis (LSS). With the aim of less invasiveness and better preservation of spinal stability. these techniques have been developed. But there are no large randomized studies to show the surgical results between these two techniques. The objective of this study was to examine the safety and efficacy of these two minimally invasive techniques. Methods : A total of 80 patients were included in this study (Group I : bilateral laminotomy, Group II : Unilateral laminotomy for bilateral decompression). Perioperative parameters and complications were analyzed. Symptoms and scores such as visual analog scale (VAS) scores, Oswestry Disability Index (ODI) scores, and SF-36 scores of prospectively accrued patients were assessed preoperatively and at 1 month and 12 months after surgery. Paired-t test, two-sample student-t tests, and non parametric tests were used to determine cross-sectional differences between two groups. Results : No major complications such as spinal instability or deaths occurred during follow-up periods. VAS, ODI scores and SF-36 body pain and physical function scores showed statistically significant improvements in both groups (p<0.001). The significant widening of the spinal canal diameter was also noted in both groups. But, in Group II. there were minor postoperative complications such as dural tear (2 cases 5.0%), fracture of ipsilateral inferior facet (1 case 2.5%), and 5 cases of transient leg symptoms of contralateral side. Conclusion : Both bilateral laminotomy and unilateral laminotomy for bilateral decompression allow achievement of adequate and long-lasting operative results in patients with LSS. But postoperative complications are more frequent in Group II (unilateral laminotomy and bilateral decompression). These results indicate that bilateral laminotomy is the preferred minimally invasive technique to treat symptomatic LSS.