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.