Purpose: To evaluate the diagnositc performance of elastography for thyroid nod- ules on the transverse and longitudinal planes. Materials and Methods: Gray scale ultrasonography (US), elastography on trans- verse and longitudinal planes, and fine needle aspiration biopsy for 78 thyroid nodules (malignant: 34 cases, benign: 44 cases) were performed. According to the Asteria cri- teria of elastography, scores 1 and 2 were classfied as probably benign and scores 3 and 4 were classifeid as suspicious. Strain ratios on transverse and longitudinal planes were measured. Sensitivity, specificity, positive predictive value, negative pre- dictive value, accuracy, and Az value (under the receiver operating characteristics curve) of elastography on transverse and longitudinal planes were calculated and compared. Results: Scores 3 and 4 were more frequently seen in malignant nodules on the longitudinal plane (p value = 0.007), but not significantly seen on the transverse plane (p value = 0.160). Sensitivity, specificity, positive predictive value, negative predictive value, accuracy, and the Az value of elastography on the longitudinal plane were high- er than those on the transverse plane, although Az values on the transverse and long- tudinal planes were not statistically significant. Conclusion: Diagnostic performance of thyroid elastography, especially sensitivity, were higher on the longitudinal plane than the transverse plane.