To compare magnetic resonance imaging (MRI), 64-slice multi-detector computed tomography (MDCT) and dual-source computed tomography (DSCT) in assessing global function parameters using a moving heart phantom. A moving heart phantom with known volumes (215-258 ml) moving at 50-100 beats per minute was examined by three different imaging modalities using clinically implemented scanning protocols. End-diastolic and end-systolic volumes were calculated by two experienced observers using dedicated post-processing tools. Ejection fraction (EF) and cardiac output (CO) were calculated and mutually compared using Bland-Altman plots. MRI underestimated the ejection EF by 16.1% with a Bland-Altman interval (B-A) of [-4.35 (-2.48) -0.60]. Sixty-four-slice MDCT overestimated the EF by 2.6% with a relatively wide B-A interval of [-3.40 (0.40) 4.20]. DSCT deviated the least from the known phantom volumes, underestimating the volumes by 0.8% with a B-A interval of [-1.17 (-0.13) 0.91]. CO analysis showed similar results. Furthermore, a good correlation was found between DSCT and MRI for EF and CO results. MRI systematically underestimates functional cardiac parameters, ejection fraction and cardiac output of a moving heart phantom. Sixty-four-slice MDCT underestimates or overestimates these functional parameters depending on the heart rate because of limited spatial resolution. DSCT deviates the least from these functional parameters compared to MRI, EBT and 64-slice MDCT.