Trust plays a significant role along the life-cycle of (electronic) participation initiatives. Based on causal roles that trust may have according to Rousseau et al. [31, p. 396] - (1) trust as condition for participation, (2) trust during participation, and (3) trust as outcome of participation - it is imperative to analyse these influential roles in order to take measures that contribute to higher trust and to reduce distrust in, and as an outcome of participation. In this regard, a literature study is performed analysing research on trust in e-government, online commerce and e-participation. Literature research unveils that analyses of trust in e-participation and their results are diverse, and a number of aspects are not studied so far (in particular ICT as a means for communication and as a tool in e-participation). This paper therefore identifies research needs along a trust model for e-participation. The aspect of guidelines for developing trustworthy e-participation tools is particularly examined by outlining various research steps. Online participatory budgeting serves as example for analysing trust, as such initiatives integrate different aspects of e-participation in the support tools.