This study aimed to compare the parametric value of T2 with and without fat suppression (FS) on T2 mapping for the evaluation of extraocular muscles (EOMs) in mild thyroid-associated ophthalmopathy (TAO).We prospectively recruited 44 consecutive patients with mild TAO seen between May 2020 and October 2022 and 26 healthy controls with no history of eye- or thyroid-related or other autoimmune diseases. Patients with mild TAO were subdivided into active and inactive groups based on their clinical activity scores. The T2 of each EOM was measured over a large and small area of interest on T2-mapping images with and without FS. Receiver operating characteristic (ROC) curves were used to evaluate the diagnostic efficacy of T2 for detecting TAO activity.The T2 was significantly and heterogeneously higher in the active group than in the inactive and control groups (P < 0.05). FS-T2-mapping images had better signal display within and at the edges of the EOMs than those without FS. It was possible to observe high-signal aggregation visible in the periphery of some EOMs, and the central part showed relatively low signals. The maximum T2 measured in small or large areas with and without FS had good diagnostic efficacy for TAO activity, with that of no-FS being better (the area under the ROC curve of the maximum T2 measured in a small area and a large area without FS was 1.0 and 1.0 and P values of < 0.001 and < 0.001, respectively).Maximal T2 with or without FS can facilitate the early clinical detection of mild TAO activity. The maximum T2 in a small area can facilitate active staging of patients with mild TAO.Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.