Background. Radioactive-iodine remnant ablation is an integral part of the papillary thyroid carcinoma (PTC) treatment. Although a minimum dose is usually recommended, there is controversy as to whether the low-dose (1100 MBq) radioactive-iodine remnant ablation is adequate for selected patients. Methods. A retrospective cohort study was conducted on 691 patients. Patients with no remnant thyroid on the follow-up whole body scan and low stimulated thyroglobulin (sTg) level (<2.0 ng/mL) were deemed as successful treatment cases. Results. Initial low-dose radioactive-iodine remnant ablation was successful in 431 patients (62.3%). Multivariate analysis demonstrated a negative correlation between successful radioactive-iodine remnant ablation and coexisting Hashimoto thyroiditis based on histopathology diagnosis (odds ratio [ OR] 53.23; p < .001) as well as elevated preablation sTg (OR51.24; p < .001). Conclusion. Our data suggest that coexisting Hashimoto thyroiditis and elevated sTg are negative predictive factors for successful low-dose radioactive-iodine remnant ablation treatment. An appropriate risk-adjusted approach may improve the efficacy of radioactive-iodine remnant ablation treatment. (C) 2015 Wiley Periodicals, Inc.