This article describes data related to a research article titled “Estimation of myocardial extracellular volume fraction with cardiac CT in subjects without clinical coronary artery disease: A feasibility study”, Kurita et al. (in press) [1]. Myocardial extracellular volume fraction (ECV) is an imaging biomarker that can elevate in various heart diseases. This article describes correlation between CT-derived and MRI-derived ECV in 24 myocardial segments in 8 patients. CT-derived ECV was obtained from pre-contrast and delayed-phase images acquired by using dual-source CT system. MRI-derived ECV was obtained by using modified Look-Locker inversion recovery sequence implemented on a 3 T MRI system.