OBJECTIVES: This study was conducted to find out topographic changes of cerebral perfusion between pretreatment and posttreatmet state via region of interest method by Single Photon Emission Computed Tomography(SPECT). METHOD: By DSM-IV criteria, we selected 32 patients with pure Attention Deficit Hyperactivity Disorder (ADHD) through various assessment scales, psychometric tools and neuropsychological batteries. All the patients with ADHD were studied by Tc99m-HMPAO Brain SPECT, before methylphenidate(MPND) treatment and after 6 weeks treatment. Three transaxial brain slices delineating anatomically defined region of interest at approximately 20, 40, 60mm above the orbitomeatal line(OML) were used, with the average number of counts for each region of interest normalized to the area of cerebellar maximal uptake. RESULTS: In the plane 20mm above OML, None of areas showed significant perfusion changes. In the plane 40mm above OML, left and right prefrontal areas, caudate and thalamic areas showed increased relative perfusion compared to pretreatment state. In the plane 60mm above OML, there were no increases in all regions of interest. CONCLUSION: The MPND treament improved cerebral blood flow in some specific brain regions: prefrontal lobe, caudate and thalamic area. We found neuroanatomical action sites of MPND might be the pathophysiologic sites of ADHD which had been proved in previous studies. These findings implied that MPND treatment could correct the underlying pathologic brain dysfunction of ADHD.