In order to discover an effective treatment for dementia it is necessary to include dementia patients in clinical research trials. Dementia patients face an increased risk to lose the capacity to consent to research participation, and research possibilities with incompetent participants are legally strictly limited. One solution is for patients to consent to research through an advance research directive (ARD) whilst still competent. In order to explore whether such a directive would be useful and valuable in practice we conducted a qualitative study (13 interviews). We explored the opinions and arguments of researchers in the field of dementia, aiming to map the possibilities and constraints of ARDs. It was argued that a positive ARD could be valuable to discuss research participation with proxies, and patients with a negative ARD will be excluded from research trials. However, it is argued that an ARD cannot replace the informed consent procedure, and in practice proxy dissent will overrule written consent. The practical use of these directives is thus limited, as most researchers will not comply with positive directives.