The ReSPECT Project (Reconceptualising Services from the Perspectives of Children and Teens) was conducted in a disadvantaged urban community in Australia, with young people who experience marginalisation and who were involved with multiple service agencies across a range of service sectors. Its purpose was to work closely with young people to understand their experiences of service engagement, their perspectives on the service priorities for young people in their area, and to support them in the development, trial and implementation of a youth led service initiative. This paper describes the methodology employed with the young people, its theoretical underpinnings, and the challenges that needed to be overcome in the conduct of this research. Critical to the ReSPECT approach is relationship building and capacity development with local service providers. This aspect of our work is also briefly described in this paper. The ReSPECT approach makes a significant contribution to the participatory methodological literature. It is distinctive from existing approaches because (1) it gives equal attention to the sustained engagement and scaffolding of young people in the development of ideas, and to the capacity building of service providers addressing organisational culture and constraints; (2) it follows the process of service change from the conceptualisation of youth-led ideas, through to development, partnership, implementation and evaluation; and (3) it is designed for engagement with marginalised young people with diverse service experiences, whose voices are so often absent from participatory projects.