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BACKGROUND: To compare 11 heartbeat (HB) and 17HB modified lock locker inversion recovery (MOLLI) pulse sequence at 3T and to establish preliminary reference values for myocardial T1 and the extracellular volume fraction (ECV). METHODS: Both phantoms and normal volunteers were scanned at 3T using 11HB and 17HB MOLLI sequence with the following parameters: spatial resolution = 1.75x1.75x10 mm on a 256x180 matrix, TI initial = 110ms, TI increment = 80ms, flip angle = 35 degrees, TR/TE= 1.9/1.0ms. All volunteers were administered Gadolinium-DTPA (Magnevist, 0.15mmol/kg), and multiple post-contrast MOLLI scans were performed at the same pre-contrast position from 3.5-23.5 minutes after a bolus contrast injection. Late gadolinium enhancement (LGE) images were also acquired 12-30 minutes after the gadolinium bolus. RESULTS: T1 values of 11HB and 17HB MOLLI displayed good agreement in both phantom and volunteers. The average pre-contrast myocardial and blood T1 was 1315 +/- 39 ms and 2020 +/- 129 ms, respectively. ECV was stable between 8.5 to 23.5 minutes post contrast with an average of 26.7 +/- 1.0 percent. CONCLUSION: The 11HB MOLLI is a faster method for high-resolution myocardial T1 mapping at 3T. ECV fractions are stable over a wide time range after contrast administration. [ABSTRACT FROM AUTHOR]