Using local authority planning in Dublin as a case study. the extent and effectiveness of community and development interests' participation in policy formulation is examined. A primary locus is on the nature and timing of participation as a determinant of the relalive influence that each can exert over policy decisions. A critical distinction is drawn between formal and informal participation channels. The vast array of informal channels available to development interests can mean that they have little need to participate formally; thus a primary and secondary layer of influence on policy formulation can be distinguished. The primary layer is largely informal, on-going and pervasive. The secondary layer is formal, controlled and capable only of adapting rather than formulating policy. This supports the existence of an incontestable basis of planning policy that emerges from the primary layer of influence and reflects an inherent acceptance of the legitimacy of development interests' demands. As a consequence, questions are raised about the role of participation within a planning system which functions in support of capital.