We report our case and review the literature on reversal DWI lesions, ADC thresholds and correlation between DWI lesion and outcome measured with clinical scales. A 30-years old woman was admitted to our hospital 18 hours after stroke onset. Considering the absence of alterations on CT and the worsening of symptomatology, the patient underwent MRI, which showed a slightly hyperintense signal in FLAIR images in the left portion of the pons and midbrain and a more evident bilateral DWI hyperintensity of the pons. The patient was treated with mechanical and pharmacological intra-arterial thrombolysis. The patient showed a rapid improvement of symptoms. Two weeks after the treatment her clinical conditions were characterized by a residual right hemiparesis and complete recovery of right motility, respiratory and swallowing difficulties. MR examination demonstrated a slight signal alteration of the pons left hemiportion and a disappearance of the mesencephalic signal alteration and of the right portion of the pons. DWI lesions represent irreversibly damaged tissue but new evidence suggests that DWI lesions may be reversible, especially with reperfusion, by now well demonstrated in animal models. Therefore acute DWI lesions probably contain not only irreversibly injured tissue but also parts of the penumbra. The debate on the capability of ADC maps to discriminate irreversibly from reversibly damaged tissue is a matter of controversy. ADC values in human stoke are not an independent indicator of tissue viability. The use of thresholds may improve reproducibility but not validity.