Penumbral tissue identification is critical for the treatment decision for patients with acute ischemic stroke. In the present study, we aimed to assess the impact of arterial spin labeling (ASL) at different post-labeling delays (PLDs) in penumbral tissue quantification, and compare their performances in patients’ selection for endovascular treatment with dynamic susceptibility contrast as reference. The results showed ASL appears to persistently overestimate penumbral tissue in acute ischemic stroke. PLD shows substantial impact on quantification of hypoperfusion volume. Long PLD, 2500ms for example, is preferable in penumbral tissue detection and patients’ selection.