Objective. The aim of this study was to compare the accuracy and efficacy of sonographically guided lumbar periradicular injections through in-plane or out-of-plane approach techniques for patients with unilateral lower lumbar radicular pain. The feasibility and accuracy of these techniques were studied by means of computed tomography (CT). Methods. A total of 46 patients with chronic unilateral lumbar radicular pain were recruited and randomly assigned to either the in-plane or out-of-plane injection group. A mixture of 3 mL 1% lidocaine and 7 mg betamethasone was injected. The visual analog scale (VAS) was used to assess pain before and after treatment. Results. The pain intensity, as measured by VAS, significantly decreased in both in-plane and out-of-plane injection groups. Conclusions. The sonographically guided periradicular injections are feasible and effective in treating lumbar unilateral radicular pain.