This special edition is a snapshot of current methodological and theoretical debates in our thinking and 'doing' of participatory research and their pivotal influence on research that involves older people with lived experience of a mental health condition, and/or dementia. Given that the International Journal of Geriatric Psychiatry has a broad audience, including health and social care professionals -psychiatrists, psychologists, social scientists, nurses, and other therapists -and neurobiological researchers, we want to present these debates through the examples of international practices and findings. Our aim in compiling this special issue is to guide and inspire the use of participatory research within applied health and social science research with older people, giving voice to what is meaningful to those with lived experience of mental health problems in later life, and challenging dominant power structures that exist within psychogeriatric research and practice. Reflecting on the edition we hope that we illustrate a breadth of topics and findings in relation to participatory work, and some of the current tensions in undertaking this kind of research.The articles gathered in this edition reflect a range of up-to-date debates about our use of participatory research and, we consider, capture a key point in an ongoing paradigm shift, and an opportunity to reflect on how we can continue to work effectively within this shift to produce innovative and useful research.Historically, people with lived experience of a mental health condition, and/or dementia have been marginalised and excluded from research and debates about their lives. However, in the last few decades, this has begun to change in many parts of the world, partly due to an increasing emphasis in policy on public involvement in research, but also, and perhaps more critically, due to the activism and self-advocacy of people with lived experience. In the UK, Heather and Ruth have both been involved in this socio-political shift in relatively instrumental ways -Heather met James McKillop in 1999, and together they established the Scottish Dementia Working Group, 1,2 and Ruth first investigated and documented the rise of dementia activism. 3 This work and the actions of people with dementia have been embedded in a critical disability studies perspective, at the heart of which is the mantra -'nothing about us without us'. It has paved the way for the participatory research we see today.Most researchers working in applied dementia research are on a quest to enable people with dementia to participate in their research.