Theoretical background: Participatory budgets (PBs) have become a widely known innovation used to engage citizens in policymaking. Since 2011, citizens in Polish municipalities can decide on how a portion of local budget can be spent. In Germany, PBs originally served the purpose of getting feedback from citizens in the context of fiscal strains. However, since about 2015, German PBs are increasingly taking after the model established in Poland, establishing fixed pools of funds. Does it present a case of between-country convergence in the functionalities of PBs and their quality? So far, such comparative questions remained mostly unanswered in the field of PB-related studies. Purpose of the article: The aim of the paper was to investigate this possibility of convergence in PB-quality by comparing the state of and changes in the quality of PBs with fixed funds between Poland and Germany. To evaluate the quality and scope of functionality of PBs, the amount of planned PB-funds per capita and participation rates (voter turnout levels) were inspected. Two research hypotheses were formulated. The first one stipulates a higher performance level of Polish PBs by the two criteria, across a variety of municipality types. The second hypothesis posits that the differences in the quality of PBs tend to diminish over time, as the latest to innovate launch their first experiments. Research methods: Works on the diffusion of PBs in both countries were reviewed to provide background for the study. Two datasets were constructed containing data on the two measures of PB-quality, the population size, and the status of innovator. The data were first compared graphically. In a later step, statistical methods were applied, including variance analysis for the two dependent variables related to PB-quality at once (MANOVA) and for each of them separately (ANOVA). Results of the study were presented and discussed in the context of interactions between innovators and potential adopters in social networks, as well as political agendas in the two countries of interest. Main findings: Research findings allowed to confirm the research hypotheses. PBs in both countries have been mostly simple innovations of limited quality, but those in Poland tended to perform better, judged by the two chosen criteria. The gap, especially for PB-funds, is closing, but that does not mean that in the course of innovators’ and regulators’ actions a unified innovation model has emerged. PBs in both countries utilize their functionalities in diverse ways, based on specific experiences and traditions in policymaking. Thus, PBs in Poland and Germany have different trajectories of development with fixed pools of funds as the simplistic innovation core that makes them highly adaptable in different policy contexts.