Participation of people living with HIV/AIDS (PLHA) has become a new standard of good governance in HIV services worldwide, and most HIV organizations make reference to it. This standard has had a considerable impact in Cambodia, where hundreds of PLHA have been recruited by organizations to participate in the development of HIV services. However, participation is a vague concept with various interpretations and applications. Drawing on ethnographic research conducted between 2006 and 2008, this article first clarifies what promoters expect from patient participation in Cambodia and then examines its meanings and uses for one category of PLHA working in hospitals (hereafter "volunteers"). It shows that volunteers have played a valuable role in the scaling-up of access to care and treatment policy, and that although international organizations in Cambodia see patient participation as empowering PLHA, these volunteers face structural violence caused by inherent conflicts within Cambodia’s strict health care hierarchy.