Summary:Neuropeptide Y (NPY) has been shown to be involved in the control of several neuroendocrine functions. Moreover, in animal models, NPY produces behavioral effects that are similar to those induced by anxiolytics. We studied NPY-like immunoreactivity (NPY-LI) in cerebrospinal fluid (CSF) in two primary degenerative dementias, Alzheimer disease (AD, n = 34) and frontotemporal dementia (FTD, n = 22) and correlated the CSF NPY-LI levels with clinical characteristics, as rated with the Organic Brain Syndrome scale. There were significant correlations between NPY-LI and such clinical items as suspiciousness, anxiousness, restlessness-agitation, and irritability in both AD and FTD. AD patients, but not FTD patients, showed a significant negative correlation between NPY-LI and duration of the disease. Thus, the study found significant correlations between CSF NPY-LI and emotional symptoms and behavior in organic dementia