The subject of this thesis is Persuasive Design (PD) used in a religious context for people with mental disabilities. I am trying to answer the questions: How can the persuasion work and where is the ethical limit to persuasion. The background for this study is my work with communicating religion to mentally disabled, my theology studies and my studies in Information Architecture/ PD at Aalborg University. Persuasion is no new theory – it goes back to the creators of Rhetoric, but what is new is the creation of persuasive technology. Combined with technology, persuasion becomes more powerful, and with a stronger persuasive power there is a need for more focus on and concern with the ethics of persuasion. When the target group is people that are weaker in judgment and easier to deceive and when the content is religious, then ethical focus and concern is even more called for. The purpose of this work is to bring forth some guiding principles for both persuasion and ethics in religious related PD for mentally disabled. I have been working with different theories on cognition, religiousness, ethics and of course PD. The main source for the PD-study is B.J. Fogg´s work described in his book: “Persuasive Technology. Using Computers to Change What We Think and Do” (2003) and in articles at his website. I have also been doing empirical studies. I worked out a PD system with a religious content and made a trial run with a selected group of people with mental disabilities. The test consisted of filming there use of the system and interviewing them afterwards. A PD system is intentional and interactive. The intention of my PD system is to assist the user maintaining a religious practice – in this instance a daily prayer. The interactive element is that the user decides for himself which elements to choose and what approach to make use of in the daily prayer. On the basis of both theories and empirical studies I´ve created my contribution to an ethical persuasion: Some boundaries for the ethical use of persuasion and some guiding principles for persuasion and ethics combined into my model: A Model of Ethical Persuasion – EP model. The conclusion of this thesis is that PD systems with a religious content can be designed for and used by people with mentally disabilities in a meaningful way – and that the systems can be both persuasive and ethically sound. In designing such systems the EP model can be a useful guide. Ethical concerns should be integrated from the very beginning of planning and designing a persuasive system (no matter the content) – this is why I call my model A Model of Ethical Persuasion. The foundation of my model is Respect and Responsibility. On this basis you can work with both persuasion and ethics, which I think should be constantly interacting with each other throughout the whole process. With respect and responsibility for the user and the content of the PD system you can work with your intention, choose the relevant persuasive tools and use them with the concern not to cross the line into unethical use. Working with A Model of Ethical Persuasion I find it´s possible to create a persuasive design with a religious content for mentally disabled that meets both the persuasive and the ethical demands. There are many possibilities to further developing the system, I´ve tested. By using additional persuasive skills such as mobility, connectivity and triggers the persuasive power can be strengthened. Combined with the ethical concern it can be beneficiary for the future users.