Background: Advance directives could be an important instrument to support a person's will once he/she is not able to consent anymore - if composed competently. A survey was conducted to identify the level of knowledge concerning possibilities and limits of advance directives.; Methods: The study was conducted as part of the Bavarian Dementia Survey (BayDem). Data were collected from January 2014 to December 2015 by structured face-to-face interviews. Study participants were persons with dementia and their informal caregivers (n = 74).; Results: In total, 66% reported having written an advance directive. Concerning the participants' knowledge about possibilities and limitations of advance directives, a lack of knowledge was noted about the possibility to revoke an advance directive. Furthermore, 70% of informal caregivers and 56% of persons with dementia were not aware of the possibility to include dementia-specific terms in the advance directive.; Conclusion: It is necessary to optimize structures for public information and education concerning the topic of advance directives for persons with dementia.