The aim of this study was to examine the association between long-term benzodiazepines (BZDs) use and the risk of dementia. Population-based nested case-control study of dementia. All subjects were aged 45 and older and enrolled in the National Health Insurance Research Database in Taiwan, 1997-2004. Cases (N = 779) were patients who were identified with dementia at least two times in their outpatient claims. They were individually matched to six comparison subjects (N = 4,626) based on age and gender. BZD usage (average dosage per year, average days per year, and cumulative dose and periods) and potential confounding comobidities, including cardiovascular and psychiatric diseases. Subjects with dementia had higher cumulative dose, longer duration of BZDs exposure, and more likelihood to be long-term BZDs users. Our findings suggest that long-term use of BZDs is associated with an increased risk for dementia, but the underlying mechanisms remain unclear, and further investigations are needed. Long-term use of BZDs should be avoided among the elderly, who may be at a higher risk for developing dementia, in addition to other health problems.