This thesis explores the role of demographic change in the evolution of inequalities in population age structures across regions of Europe. It strives to increase our understanding of the demographic processes that shape regional population age structures, and how these processes are interrelated with regional economic development. The analysis is focused on changing relative differences over time, i.e. convergence or divergence. The focus on convergence or divergence in population age structures is a relevant subject interesting not just to the demographers, who are anyways obsessed with population dynamics. The study period, which spans from the beginning of 2003 to end of 2012, happens to be uniquely interesting because it includes major shifts both in economies and population age structures. First, in 2004 happened the biggest enlargement of European Union that largely affected economic prospects of the newly admitted countries of Central and Eastern Europe and radically reshaped the intra-European migration landscape. Second, Europe was heavily and unevenly stricken by the economic crisis of 2008-2009, which affected all domains of people's lives including behaviours directly related to demographic events. Finally, the second part of the study period was marked with the accelerated graying of relatively large baby-boom generation cohorts that started to leave the working age in 2010s changing the population age compositions faster than ever before.