The dissertation is a first attempt to explore democracy assistance efforts provided by a young democracy that was a recipient of similar aid in the past. The study investigates approaches to democracy assistance, reasons for a young democracy's engagement, methods and effectiveness of efforts to promote democratic ideas and practices in recipient countries. Specifically, the research examines how government and social actors in a young democracy conceptualize democracy assistance and how their view on democracy aid is different from approaches used by Western donors. Then, why and how a former recipient country goes about assisting other states in their struggles for democracy are investigated. Finally, the research is motivated by the question of how democracy assistance efforts by a young donor can be evaluated in terms of their potential to diffuse democracy to other recipient countries. This project demonstrates several main findings based on comparative case studies of Polish democracy assistance to Ukraine and Belarus. These conclusions contribute to the theory and practice of democracy assistance. First, the Polish approach to democracy assistance takes into account the political situation of recipient country and is carefully crafted when directed to authoritarian and democratic regimes in terms of types of assistance, choice of domestic partners, and strategies used in the programs. This assistance also seems to avoid pitfalls described in the literature on democracy assistance. Second, this dissertation reinforces the importance of civil society as a sender and recipient of democracy assistance. This study unveils the key role of Polish NGOs in shaping the state's democracy assistance and their unique ability to reach civil society groups in recipient Belarus and Ukraine. Third, this research reveals a great deal about the features of cross-border work as a method of democracy assistance to exert an impact on civil society groups. Polish NGOs engage in close collaborative work with foreign civil society groups. By demonstrating the democratizing potential of cross-border projects, the dissertation shows that this form of assistance may contribute to the overall diffusion of democracy in the region, thus strengthening the role of regional actors in promoting democratic values and practices.