With arterial spin labeling (ASL) MRI, the delay time between labeling and image acquisition is a critical imaging parameter for accurate flow quantification. Multi-delay ASL has been proposed to tackle the problem of unknown arterial transit time (ATT). However, it is not fully understood how the range of delay times affects the derived CBF. The present study aimed to investigate this potential issue. Results show that the CBF derived from multi-PLD ASL varies with the choice of PLD (overestimated when the PLD range does not cover ATT) as well as SNR (overestimated along with greater variability when SNR is low).