[en] We report a clinical case of a new type of discrepancy between two tracers usable for brain functional imaging: the Xenon 133 and the HmPAO-^99mTc. A 66 year old men had presented a brutal left hemiplegia with transient troubles of consciousness in relation with a right protuberant infarct without hemispheric lesions. The functional studies were performed 4 months after the onset, successively by the Xe inhalation method and immediately after the HmPAO study. On a patient kept still on the camera bed when cerebral blood flow (CBF) study depicted both a right cerebellar low flow and a slightly decreased CBF in the controlateral hemisphere ('hemispheric diaschisis'), the HmPAO SPECT was normal. This observation illustrates both the crossed hemispheric diaschisis and a new type of discrepancy: indeed, the known cases were until now in relation with alterations of the blood: brain barrier, which doses not exist in our report. The explanation of this type of discrepancy remains unclear but is probably linked with the HMPAO retention mechanisms. (author)