Introduction <p>Degenerative lumbar spinal stenosis frequently requires surgical intervention when conservative treatments fail. Minimally invasive techniques such as unilateral laminectomy for bilateral decompression have largely replaced traditional open laminectomy because of effective decompression and reduced tissue damage. This study compared the radiological and clinical outcomes of tubular decompression and unilateral biportal endoscopy (UBE) in patients with severe stenosis.</p> Methods <p>This was a retrospective, monocentric, nonrandomized study including 103 patients with severe lumbar spinal stenosis (52 tubular decompression, 51 UBE) from July 2020 to April 2024. The primary radiological outcomes were changes in anteroposterior diameter and dural sac surface area, assessed by MRI. Clinical outcomes included operative time, complication rates, and patient-reported outcomes with the Oswestry Disability Index and visual analog scale for pain, evaluated preopertatively, 3 and 12 months postoperatively.</p> Results <p>As compared with tubular decompression, UBE resulted in a more significant increase in anteroposterior diameter (+ 4.9 vs. + 3.75&#xa0;mm, <i>p</i> &lt; 0.001) and dural sac surface area (+ 95.8 vs. + 85.4&#xa0;mm², <i>p</i> = 0.038). However, with both techniques, clinical improvements were similar at 3 and 12 months, with no significant difference in Oswestry Disability Index, visual analog scale score, or patient satisfaction. The complication rate, including reoperation, was low in both groups, but the incidence of symptomatic hematoma was higher with UBE than tubular decompression.</p> Conclusion <p>Both tubular decompression and UBE were effective for spinal stenosis treatment, with UBE providing superior radiological decompression, even in the early learning phase. However, the techniques were comparable in clinical outcomes at 3 months and 1 year. Further studies are needed to assess long-term results and refine patient selection criteria.</p>