Objective: The aim of this prospective study was to evaluate pre- and post-treatment MRI and CT findings of osteoid osteoma (OO) patients treated with radiofrequency thermo-ablation (RFTA) and to compare these findings with visual analog scale (VAS) scores. Methods: Sixteen patients (4 females and 12 males; mean age of 18.87 ± 8.75 years (range: 8e37)) with OO were examined with CTand MRI, at baseline and at an average of 3 months following the procedure. On pre- and post-procedural CT and MRIs, OO-related findings were recorded. Treatment success was evaluated with VAS scores. Results: Baseline VAS scores were 8 or 9 and follow-up scores were 0 or 1, indicating no early recurrences. Nidus diameters decreased significantly after the procedure (p ¼ 0.027, p ¼ 0.002, and p ¼ 0.002; and p ¼ 0.001, p ¼ 0.001, p ¼ 0.001 for AP, ML and CC nidus diameters for CT and MRI, respectively). The mean nidus volume were significantly decreased after the procedure (p ¼ 0.001, for CT and MRI). On post-procedural images, cortical thickening, the signal intensity and contrast enhancement of the nidus and the extent of periostitis were significantly decreased (p ¼ 0.019, p ¼ 0.001, p ¼ 0.001 and p ¼ 0.034, respectively). There was no significant change in nidus calcification, perinidal cortical and intramedullary sclerosis, periosteal reaction, bone deformity, bone marrow and soft tissue edema, joint effusion and synovitis after the procedure (p ¼ 0.253, p ¼ 0.062, p ¼ 0.245, p ¼ 1, p ¼ 1, p ¼ 0.429, p ¼ 0.371, p ¼ 0.625, p ¼ 1). Conclusion: Although the changes in imaging findings may be helpful in early follow-up of OO patients treated with RFTA, these changes alone cannot be used with accuracy in predicting treatment response. Level of Evidence: Level IV, Therapeutic Study.