The article deals with the institutional conditions for the social innovation development. From the theoretical perspective, the relevant key points are very poorly developed. Thus, the aim of this study is to identify trends in the sustainable development of social innovation initiated by citizens. In this context, the author's interpretation of social innovation is given, and a list of exogenous and endogenous factors affecting the socio-innovative development is introduced. Exogenous factors were grouped as involving the following ones: public administration, socioeconomic conditions, development of human capital, innovation infrastructure, informal institutional environment. Endogenous factors were divided into 2 groups, characterizing the processes of social innovation and resource support. For the present research, a questionnaire has been developed, including closed-ended questions on the features of the development of social and innovative projects. As the research findings, endogenous and exogenous linear models with two or three independent variables are suggested by the authors, showing how the features of national and regional economies affect the results of social and innovation activities. The results indicate that such factors as the number of personnel engaged in R&D, social payments, and taxable income have a positive impact on the budget of small and medium social innovation. Furthermore, the link between the large social innovation budget, on the one hand, and the number of personnel engaged in R&D, and investment potential of the region has been revealed. The research findings show a trend of development of social innovation initiated by citizens. The major practical contribution of the research is that it provides the possibility of the research findings to be used by the state authorities to implement effective policies that will facilitate social innovation development.