Abstract
This study explains why Brno’s municipal participatory budgeting (PB) has become durably institutionalised and scaled, whereas Bratislava’s remains fragmented. National fiscal and programme-budgeting frameworks are treated as moderating conditions that enable or constrain local design choices, not as the primary object of analysis. Using a most-similar systems logic, we conduct a comparative multi-case analysis with embedded units – annual PB cycles, project types, core institutions/platforms, and, for Bratislava, boroughs. Evidence derives from publicly available municipal legal and budgetary documents and formally adopted PB rules and reports. The analysis integrates mechanisms from institutional theory (institutionalisation), actor – network theory (socio-technical robustness of identity, workflow, and data infrastructures), deliberative democracy (input/throughput/output legitimacy), and principal – agent perspectives (transparency and auditability). Findings show that Brno’s stable funding envelope, dedicated participation unit, codified cycles, secure digital identity, and auditable end-to-end pipeline underpin predictable delivery despite clustered turnout. Bratislava’s borough-led PB enables experimentation but creates coordination frictions, heterogeneous rules, and uneven links to programme budgeting. The study offers a portable, mechanism-based diagnostic for post-socialist municipal contexts.