Hypoperfusion in acute stroke can be detected without exogenous contrast agents using BOLD delay. However the effect of scan duration on assessing perfusion using this method hasn’t been systematically evaluated. This study researched the effect of different scan lengths on diagnostic accuracy and image quality of BOLD delay maps while accounting for head motion. Our results revealed that scan time can be reduced to 3 min and 24 sec without compromising diagnostic power and image quality. However, lesion volumes were robust down to a scan length of 1 min and 8 sec.