Purpose The purpose of this paper is to present a systematic literature review of empirical studies into online platforms for political participation. The objective was to diagnose the relationship between different types of digital participatory platforms, the real possibilities of participation generated by those initiatives and the impact of such participation on the decision-making process of governmental representatives. Design/methodology/approach A systematic literature review was conducted using pre-defined terms, expressions and criteria. A total of 434 articles from 1995 to 2015 were gathered from the Web of Science database. And, 32 studies were selected from those articles for meta-synthesis, and the cases investigated were evaluated according to the e-participation ladder model (Smyth, 2001). Findings The results indicated that online political participation worldwide remains timid both in quantity and quality. We have witnessed the growth of a kind of "rhetorical participation" promoted by policy-makers and the rise of a "participatory despotism", in which only the privileged partake, while the majority remains silent. Practical implications - The solutions found to promote increased participation and ensure its effectiveness ranged from shaping the platform design in accordance with citizens' capacities and interests to a need for profound political-administrative change, which includes the world's public agencies adopting a more transparent, inclusive and collaborative approach to decision-making. Originality/value This paper proposes a systematic review, mapping the studies on online platforms for political participation, analysing the questions, methods and conclusions found by the authors and evaluating each case study with a participation ladder.