This article deals with the problem of political participation and public sphere learning by adolescents during the mass protests in contemporary Russia and Ukraine. Referring to theories of contentious politics and the public sphere in the post-communist world, the author highlights the debate around the relations between private and public in this context: is the value of public participation formed in the private sphere and then translated into a public one? Or rather, is the public realm something opposite to the private? Using in-depth biographical interviews with the adolescents participating in the Bolotnaya and Maidan movements, the author considers this dilemma through the lens of activists’ socialization. The analysis discovers that there is no direct connection between the values of private independence and public freedom during the growing-up process of adolescent activists. The values of private independence appropriated by Russian adolescents do not automatically translate into practices in the public sphere, and, conversely, Ukrainian activists strongly adhere to an ethic of political freedom, but to do it they prefer to break with the values of the private sphere rather than transfer them into politics. To conclude, the author discusses some implications of the analysis of political participation of adolescents on how notions of private and public are composed in Russia and Ukraine.