Objective@#To compare native and post-contrast T1 mapping with late gadolinium enhancement (LGE) imaging for detectingand measuring the microvascular obstruction (MVO) area in reperfused acute myocardial infarction (MI). @*Materials and Methods@#This study included 20 patients with acute MI who had undergone 1.5T cardiovascular magneticresonance imaging (CMR) after reperfusion therapy. CMR included cine imaging, LGE, and T1 mapping (modified look-lockerinversion recovery). MI size was calculated from LGE by full-width at half-maximum technique. MVO was defined as an areawith low signal intensity (LGE) or as a region of visually distinguishable T1 values (T1 maps) within infarcted myocardium.Regional T1 values were measured in MVO, infarcted, and remote myocardium on T1 maps. MVO area was measured on andcompared among LGE, native, and post-contrast T1 maps. @*Results@#The mean MI size was 27.1 ± 9.7% of the left ventricular mass. Of the 20 identified MVOs, 18 (90%) were detectedon native T1 maps, while 10 (50%) were recognized on post-contrast T1 maps. The mean native T1 values of MVO, infarcted,and remote myocardium were 1013.5 ± 58.5, 1240.9 ± 55.8 (p < 0.001), and 1062.2 ± 55.8 ms (p = 0.169), respectively, whilethe mean post-contrast T1 values were 466.7 ± 26.8, 399.1 ± 21.3, and 585.2 ± 21.3 ms, respectively (p < 0.001). The meanMVO areas on LGE, native, and post-contrast T1 maps were 134.1 ± 81.2, 133.7 ± 80.4, and 117.1 ± 53.3 mm2, respectively.The median (interquartile range) MVO areas on LGE, native, and post-contrast T1 maps were 128.0 (58.1–215.4), 110.5(67.7–227.9), and 143.0 (76.7–155.3) mm2, respectively (p = 0.002). Concordance correlation coefficients for the MVO areabetween LGE and native T1 maps, LGE and post-contrast T1 maps, and native and post-contrast T1 maps were 0.770, 0.375,and 0.565, respectively. @*Conclusion@#MVO areas were accurately delineated on native T1 maps and showed high concordance with the areas measuredon LGE. However, post-contrast T1 maps had low detection rates and underestimated MVO areas. Collectively, native T1 mappingis a useful tool for detecting MVO within the infarcted myocardium.