Background: With the increasing use of multidetector computed tomography, the reported hypertrophic cardiomyopathy (HCM) or thickened interventricular septum (IVS) has increased. However, there are not sufficient data regarding the real clinical value of the cardiac CT IVS thickness measurements in the real world. Purpose: To evaluate CT reports of HCM in adults and correlate them with conventional echocardiography Method: We performed a retrospective review, from March 2009 to May 2011, of cardiac CT reports containing diagnoses or suggestions of HCM in our electronic medical records. A total 157 reports were found. After ruling out 28 cases (pure apical HCM in 16, no echocardiography in 12), we analyzed 129 cases of CT-scan-based thickened IVS reports and compared those numbers with numbers derived from corresponding echocardiograms. The IVS numbers all came from the original reports; in some cases, the other missing numbers were measured retrospectively by another physician based on the original CT and Echo images. Results: A total of 129 cases, mean age 65짹13 years, 71 male cases (55%). A paired sample t-test revealed a significant difference in the IVS thickness (p<0.001), posterior wall (PW) thickness (p=0.001), left ventricular end-diastolic dimension (p=0.001) between the CT and Echocardiogram (Table). We calculated the IVS/PW ratio which showed a significant difference between the two (p<0.001, paired t-test). Finally, using the IVS/PW ratio ��� 1.3 as the cut-off value of HCM, the CT scan revealed HCM in 108 cases (83.7%); echocardiography, 18 cases (14.0%) (Chi-square, p=0.043). A measure of agreement (Kappa) was 0.061. Conclusion: The IVS thickness measured by cardiac CT was larger than that of conventional echocardiography--CT���s low frame rate (compared to echocardiography) makes it much more likely to miss the moment of full end-diastolic extension, which then implicitly overestimates IVS thickness.