AIM Results on determinants of benzodiazepine (BZD) use in general and inappropriate use were inconsistent and mostly univariate. The relative importance of sociodemographic, psychological and physical determinants has never been investigated in a comprehensive, multivariate model.METHODS We included 429 BZD users and 2423 non-users from the Netherlands Study of Depression and Anxiety (NESDA) in order to investigate sociodemographic, psychological and physical determinants of BZD use and inappropriate use by logistic and linear regression analyses.RESULTS BZDs were used by a considerable proportion of the 2852 NESDA participants (15.0%). BZD use was independently associated with older age, singleness, unemployment, treatment in secondary care, higher medical consumption (more severe) anxiety, depression (OR [95% CI]= 1.95 [1.29, 2.93]), comorbidity, insomnia, SSRI (OR [95% CI]= 2.05 [1.55, 2.70]), TCA and other antidepressant (OR [95% CI]= 2.44 [1.64, 3.62]) use. Overall, BZD use was rarely in accordance with all guidelines, mainly because most users (82.5%) exceeded the recommended duration of safe use. Inappropriate use was independently associated with older age (β= 0.130) and chronic illnesses (β= 0.120). Higher scores on agreeableness were associated with less inappropriate use.CONCLUSIONS Mentally or physically vulnerable subjects were most likely to use BZDs. The most vulnerable (i.e. the old and physically ill) BZD users were at highest risk of inappropriate BZD use. Without further evidence of the effectiveness of BZDs in long-term use, caution in initiating BZD prescriptions is recommended, particularly when patients are chronically ill and old, as those are most likely to display inappropriate use. © 2011 The Authors. British Journal of Clinical Pharmacology © 2011 The British Pharmacological Society.