Ferumoxytol is a blood-pool-bound superparamagnetic iron-oxide particle (SPIO) that has been shown to yield CBV-dominated fMRI contrast in humans. Differences in impulse-response (IR) timing were previously demonstrated in animals when comparing SPIO-fMRI to BOLD-fMRI. Since BOLD IR is known to differ between humans and animals, we aimed to repeat this SPIO-fMRI to BOLD-fMRI comparison in humans. SPIO-fMRI was performed in human visual cortex and IR was compared to BOLD data from the same subjects. Shorter stimulus onset time and time-to-peak were found. Stimulus design minimized neuronal interaction effects between stimuli; residual inter-stimulus interaction effects, presumably vascular in origin, were found to be minor in SPIO-fMRI, on the same scale as in BOLD.