['Dynamic perfusion-CT (PCT) with deconvolution requires an arterial input function (AIF) for postprocessing. In clinical settings, the anterior cerebral artery (ACA) is often chosen for simplicity. The goals of this study were to determine how the AIF selection influences PCT results in acute stroke patients and whether the ACA is an appropriate default AIF.', 'We retrospectively identified consecutive patients suspected of hemispheric stroke of less than 48 h duration who were evaluated on admission by PCT. PCT datasets were postprocessed using multiple AIF, and cerebral blood volume (CBV) and flow (CBF), and mean transit time (MTT) values were measured in the corresponding territories. Results from corresponding territories in the same patients were compared using paired t-tests. The volumes of infarct core and tissue at risk obtained with different AIFs were compared to the final infarct volume.', 'Of 113 patients who met the inclusion criteria, 55 with stroke were considered for analysis. The MTT values obtained with an "ischemic" AIF tended to be shorter (P=0.055) and the CBF values higher (P=0.108) than those obtained using a "nonischemic" AIF. CBV values were not influenced by the selection of the AIF. No statistically significant difference was observed between the size of the PCT infarct core (P=0.121) and tissue at risk (P=0.178), regardless of AIF selection.'] Is the anterior cerebral artery an appropriate arterial input function for perfusion-CT processing in patients with acute stroke?