Idiopathic normal pressure hydrocephalus (iNPH) is a syndrome characterized by gait disturbance, dementia, and/or urinary incontinence without causative disorders, and ventricular enlargement due to disturbed CSF circulation. The diagnosis of iNPH in the elderly remains a substantial issue, and the treatment is not always adequately provided. Many patients with possibly curable INPH often are misdiagnosed as having AD or vascular dementia. Recognition of INPH in those patients is of great importance. Here, some key clinical and neuroimaging features distinctive from other dementia are discussed. Also reviewed are the results of the recently completed prospective cohort study of iNPH (Study of iNPH on Neurological Improvement: SINPHONI). In SINPHONI, the MRI-based diagnosis (dilated ventricles associated with narrow dorsal subarrachnoid space) and ventriculoperitoneal shunt with Codman Hakim programmable valve shunt system were validated against 1-year post-surgery outcome.