Changing views of children and childhood have resulted in an increased focus on the nature of children's participation in research. Rather than conducting research on children, many researchers now seek to engage with children in research. Such a change recognises children's agency as well as their rights to have a say in matters that affect them. Research that reflects a participatory rights perspective and respects children's agency must be based on children making informed decisions about their participation. However, prevailing views of children's competence to make these decisions often preclude their involvement. While recognising the importance of informed consent from parents/guardians, we argue the importance of assent as a means of recognising the wishes of young children in relation to research participation. In this context, assent is defined as a relational process whereby children's actions and adult responses taken together, reflect children's participation decisions.