Population and the quality of labor force are the “strengths” features’ that ensure socio-economic development of a country. The last decades can be characterized as a transitional period, in which countries of European Union and especially the countries of Central and Eastern Europe are facing a demographic decline. Reduced birth rate, ageing and migration are factors’ which create a lot of pressure, both on labor market and public pension systems, items correlated with the population structure. In this paper we have presented the demographic situation and the size of migration in five countries of Central and Eastern Europe. The direct linkage between population structure, labor market and public pension systems represents, in transitional context, a threat to budget sustainability, especially in Romania. We consider that the reformation has to be adjusted with the new socio-economic conditions, finding new solutions for increasing birth rate, decreasing the “exodus” of young population and stimulating economic activities.