ENAdequate social security system is one of key elements of any modern society. Retirement pensions are usually attributed to the area of social security and – as such – pension system has multiple objectives, for example, to smooth income during lifetime of individual, to address poverty issues and similar. Due to ageing population and other circumstances many countries face difficulties when providing retirement pensions solely as part of social security system. Lithuania is not an exception, so – as in many other European countries – pension reform was implemented during the period of 2003 – 2004. Design of retirement pensions before and after reform is presented in this paper. Impact of reform for estimated amount of pensions and public finances as well as main areas of uncertainty are discussed.