Objective: To evaluate thoracic periaortic adipose tissue (TAT) volume in patients with subclinical hypothyroidism (SH) in comparison with controls and in relation to cardiovascular risk factors. Methods: The study population consisted of 28 newly diagnosed SH patients (mean (S.D.) age: 37.3 (G11.4) years, 85.7% were females) and 37 healthy volunteers (mean (S.D.) age: 35.3 (G10.7) years, 81.5% were females). Comparisons between patient and control groups used demographic characteristics, anthropometrics, and laboratory findings. All participants underwent thoracic radiographic assessment in the supine position, using an eight-slice multidetector computed tomography scanner and TAT volume was measured. Results: The TAT volume was determined to be 27.2 (G12.7) cm 3 in the SH group and 16.3 (G8.1) cm 3 in the control group, and the difference was statistically significant (P!0.001). In addition, TSH levels were significantly higher in the patient group compared with the control group (P!0.001). A significant correlation was also found between TSH levels and TAT volume (rZ0.572; P!0.001). In SH patients, no significant difference was noted in TAT levels with respect to sex (PZ0.383) or concomitant smoking status (PZ0.426). Conclusions: Our findings indicate that SH patients have significantly higher TAT values than controls and that increased TAT levels correlate with increased TSH levels.