In this study, we investigated differences between gray matter and white matter perfusion in patients with a unilateral occlusion of the internal carotid artery (ICA) with dynamic susceptibility contrast. Seventeen patients and 17 control subjects were studied, using T2*-weighted gradient echo acquisition. Gray and white matter regions were obtained by segmentation of inversion recovery MRI. Lesions were excluded by segmentation of T2-weighted MRI. In the symptomatic hemisphere, cerebral blood volume was increased in white matter (P < .05) but not in gray matter. No cerebral blood flow changes were found. All timing parameters (mean transit time [MTT], time of appearance, and time to peak) showed a significant delay for both white and gray matter (P < .05), but the MTT increase of white matter was significantly larger than for gray matter (P < .05). These findings indicate that differentiation between gray and white matter is essential to determine the hemodynamic effects of an ICA occlusion.