This study was performed in order to compare the functional imaging by 99m Tc-HMPAO brain SPECT with structural neuroimaging by CT or MRI. Eighteen patients with diffuse axonal injury underwent HMPAO brain SPECT(18), CT(9) and MR(14), and neurological status were then evaluated. Seventeen patients(94%) were revealed abnormal SPECT whereas nine patients(50%) demonstrated abnormal CT compared with ten patients(71%) demonstrated abnormal MRI. The neurololgical deficits correlated well with abnormal SPECT lesion except in one case. It is therefore concluded that brain perfusion SPECT is not only more sensitive than CT or MRI, it is also more cost effective and clinically well correlated in diffuse axonal injury patient.