Epidural steroid injections may offer little-to-no short-term benefit in the overall population of patients with symptomatic spinal stenosis compared with lidocaine alone. We investigated whether imaging could identify subgroups of patients who might benefit most. A secondary analysis of the Lumbar Epidural Steroid Injections for Spinal Stenosis prospective, double-blind trial was performed, and patients were randomized to receive an epidural injection of lidocaine with or without corticosteroids. Patients (n = 350) were evaluated for qualitative and quantitative MR imaging or CT measures of lumbar spinal stenosis. The primary clinical end points were the Roland-Morris Disability Questionnaire and the leg pain numeric rating scale at 3 weeks following injection. ANCOVA was used to assess the significance of interaction terms between imaging measures of spinal stenosis and injectate type on clinical improvement. There was no difference in the improvement of disability or leg pain scores at 3 weeks between patients injected with epidural lidocaine alone compared with corticosteroid and lidocaine when accounting for the primary imaging measures of qualitative spinal stenosis assessment (interaction coefficients for disability score, -0.1; 95% CI, -1.3 to 1.2; P = .90; and for the leg pain score, 0.1; 95% CI, -0.6 to 0.8; P = .81) or the quantitative minimum thecal sac cross-sectional area (interaction coefficients for disability score, 0.01; 95% CI, -0.01 to 0.03; P = .40; and for the leg pain score, 0.01; 95% CI, -0.01 to 0.03; P = .33). Imaging measures of spinal stenosis are not associated with differential clinical responses following epidural corticosteroid injection.