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Objective: After 131 I treatment in patients with differentiated thyroid carcinoma (DTC), we sometimes find a star-shaped intense uptake of 131 I on therapeutic whole body scans (Rx-WBS), called star artifacts. Therefore, we analyzed the relevant clinical factors and prognostic value of star artifacts in DTC patients., Methods: 809 DTC patients who received 131 I treatment were retrospectively evaluated and divided into 2 groups of patients with and without star artifacts. We evaluated the therapeutic response which was divided into excellent response (ER), biochemical incomplete response (BIR), indeterminate response (IR), and structural incomplete response (SIR). Clinical factors for the presence of star artifacts were analyzed. We also compared the rate of ER, BIR, IR, SIR and recurrence rate between group 1 and group 2., Results: The major clinical factors included stimulated thyroglobulin (sTg)>1.8ng/ml, 24h radioiodine uptake (RAIU)>2.2%, and positive 99m TcO4 - thyroid imaging for the presence of star artifacts. In patients with sTg levels>10ng/ml, patients in group 1 had a higher rate of ablation success and ER than patients in group 2 (80.2% vs 65.6%, P=0.038, 31.6% vs 13.1%, P=0.008, respectively) and had a similar rate of BIR, IR, SIR. Recurrence rate was similar between group 1 and group 2 (5.2% vs 3.1%, P=0.13)., Conclusion: More remnant thyroid tissue is one of the factors associated with the presence of star artifacts on Rx-WBS. Patients with star artifacts exhibit a better therapeutic response (ER) when sTg levels are >10ng/ml. However, star artifacts have no effect on the recurrence rate., (Copyright © 2020 Sociedad Española de Medicina Nuclear e Imagen Molecular. Publicado por Elsevier España, S.L.U. All rights reserved.)