Methods: In this retrospective study, we reviewed 37 IL and 34 CL approaches. Postoperative magnetic resonance imaging of the segment involved was carried out on the same day as the operation for comparison with preoperative imaging. Radiological assessments of recess angle, recess height, facet length, and recess dural sac diameters were compared. In addition, pre- and postoperative Visual Analog Scale (VAS) pain scores for the lower limb were analyzed. Results: For IL versus CL approaches, we observed statistical differences in the postoperative recess angle (36.0° vs. 43.7°), recess height (4.27 vs. 5.06 mm), and the dural sac expansion ratio for recess diameter (1.54 vs. 2.17). There was better preservation of facet length in the CL approach than in the IL approach (91.9% vs. 83.7%). There was no difference in VAS improvement between the groups (69.3% vs. 63.6%). Conclusions Unilateral biportal decompression via the CL interlaminar approach may offer better lateral recess clearance and facet preservation than can be achieved via the IL approach. Larger-scale studies are needed for better delineation and for correlation of radiological features with clinical manifestations.