OBJECTIVES: The aim of this study are clinical application of perfusion computed tomography (perfusion CT) in hydrocephalus and comparison its cerebral blood flow parameters with transcranial doppler (TCD) and clinical outcome. METHOD: 25 patients with hydrocephalus took pre- and postoperative perfusion CT and TCD. 15 patients without neurologic deficit were also examined with same protocol as a control. Blood flow parameters of perfusion CT, such as cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) were analyzed according to clinical status and postoperative outcome. So did the TCD parameters, mean flow velocity (mFv) and pulsatility index (PI) with regard to clinical outcome. RESULTS: Perfusion CT parameters of the hydrocephalus showed decrease in CBF (gray matter P=0.035, periventricular region P=0.042) and increase in MTT (gray matter P=0.039, periventricular region P=0.045) compared to control. In postoperative improvement group, there noted reversal of perfusion parameters close to those of the control. TCD parameters showed increase in mFv (P=0.047), and decrease in PI (P=0.042) in cases with improvement. CONCLUSION: Perfusion brain CT and TCD can used as clinically useful tools to predict the postoperative outcome on hydrocephalus.