The chapter offers a comprehensive analytical framework for the study of administrative capacity and administrative capacity-building in the Cohesion Policy domain. This includes individual, organisational, and socio-economic levels of analysis. The authors examine the administrative processes for Structural Funds implementation in four case study regions in Italy (Puglia, Sicilia) and Poland (Malopolskie, Pomorskie). Based on semi-structured interviews conducted with civil servants and key stakeholders at the regional level, the chapter presents the key variables (both administrative and institutional) which have an impact on the Managing Authorities’ performance. Finally, the paper outlines the ‘lessons learnt’ from the implementation of EU Cohesion Policy in these regions.