We evaluated native T1 and extracellular volume (ECV) of the breast using modified Look-Locker inversion recovery (MOLLI) sequence and compared those between invasive ductal carcinoma (IDC) and fibroglandular tissue. Moreover, we investigated the relationship between ECV and apparent diffusion coefficient (ADC) in IDC. Our results showed that ECV of IDC was significantly higher than fibroglandular tissue, whereas there was no significant difference in native T1 between both tissues. In addition, there was no significant correlation between ECV and ADC in IDC. ECV measurement using MOLLI may provide new and more detailed information in breast cancer.