Three-dimensional reconstruction from N-isopropyl-p-[123I]iodoamphetamine (IMP) tomography has been applied clinically to the detection of perfusion defects in 22 cases (15 cerebrovascular diseases and 7 normal controls confirmed by CT and MRI), with data being analyzed in terms of receiver operating characteristic curves (ROC). The results showed that three-dimensional (3-D) image could make better diagnostic capability especially in inexperienced examiner and that it was useful decreasing of difference of diagnostic capability. 3-D image could be taken within 1 minute and 15 seconds. We concluded that the three-dimensional brain imaging with IMP using this system was clinically useful because examiner could easily diagnose perfusion defects.