With the recent upgrade of the MRI system, it has become possible to use 3D arterial spin labeling (3D ASL), which is an MR perfusion imaging technique without use of any contrast material. In this paper, we report the effects of imaging conditions on the cerebral blood flow (CBF) level (the amount of cerebral blood flow per unit brain tissue〔ml/min・100g〕) . We also report our clinical experience with 3DASL. In respect of the imaging conditions, changes in CBF values were examined when the arm and the number of excitations (NEX) were variable. The results showed that there were no significant differences in CBF values between different regions in the brain. This was due probably to the fact that the spin of the labeled blood was unaffected although the arm influenced the spatial resolution of images and NEX affected SN ratio.