Background —Reduced apparent diffusion coefficients (ADCs) correlate with cerebral ischemia. The combination of ADC with techniques to measure cerebral perfusion may help to assess the effect of treatment. Case Description —The authors describe a patient who experienced an acute stroke with hemianopia, consequently treated with intravenous recombinant tissue plasminogen activator. Positron emission tomographic imaging and MRI, including diffusion-weighted MRI, were performed during and shortly after treatment with recombinant tissue plasminogen activator and 34 to 35 hours later. Cerebral perfusion of the left occipital region was reduced to 74%. Diffusion-weighted MRI detected a territory of restricted water movement in the corresponding area. Further magnetic resonance sequences did not show any pathologies. In follow-up, positron emission tomography demonstrated reperfusion. The volume of diffusion and ADC abnormalities detected by MRI decreased markedly. A few hours later, the patient recovered completely. A third MRI examination 10 days later showed normal findings. Conclusions —In a patient with prolonged reversible ischemic neurological deficit, resolution of early diffusion changes corresponded to cerebral reperfusion and to the recovery of clinical symptoms.