Lithuania has limited domestic energy resources, and is therefore, heavily dependent on imports of oil products and natural gas. Lithuania imported around 90% of its oil and 100% of natural gas in 2009. Particularly, after the accession to the European Union (EU), and decommissioning of main electricity generation source Ignalina Nuclear Power Plant (NPP), energy security became one of the main concerns. Therefore, it is vital to evaluate different pathways the country could take in order to achieve desirable energy security, and ensure sustainable development of the energy system in Lithuania. The study was conducted using LEAP, the Long range Energy Alternatives Planning System, to develop energy policy analysis. Different scenarios presented in the report show how Lithuanian energy system would react in given different circumstances. Moreover, it demonstrates how implementation of existing energy projects separately or combined together would affect the level of energy security and sustainability in Lithuania. The research shows that current government policies could lead Lithuania to more secure and sustainable energy future. However, in a long run higher investments in renewable energy might be more environmentally and economically competitive alternative.