The research presented below is a pilot study within the framework of a project aimed at solving a research and practical problem related to studying the effectiveness of digital urban services in terms of an ecosystem approach based on the case of St. Petersburg, Russia. The aim of the study is to determine the possibilities of empirical modeling of the digital services ecosystem at various levels of urban governance (primarily, municipal), in contrast to the currently dominant attention to the study of media platforms and technological tools. To categorize e-participation services, we have used as the base the methodology by the United Nations EPI index consisting of e-information, e-consultation, and e-decisions. Each municipality of St. Petersburg was studied to identify all available e-participation resources taking into account the media type, that is, official (deployed by municipal authorities), public (deployed by non-governmental organizations), and personal (deployed by private persons). In doing so, we distinguished three types of e-participation technologies (and respective media environments) in the form of Internet websites, pages on social networks, and mobile applications. The types of services are divided into services of information, cooperation, and participation in decision-making. Based on empirical data collected on the basis of 10 pilot municipalities, the authors tried to develop a model of an ecosystem of interaction between citizens and authorities, highlighting technically different types of main media and communication environments, namely, the environment of websites (portals), the environment of social networks, and the environment of mobile platforms. The authors developed and tested a methodology that made it possible to inventory digital services of interaction between the government and citizens, depending on the level of their territorial and administrative localization, in the context of the relevant media environments.