This article presents an analysis of the developments in Lithuania's security and defence policy (LSDP) since 1990, and makes an attempt at clarifying its main tendencies and prospects. Lithuania's SDP has been mainly shaped by the concerns of re-establishing the country's statehood and state sovereignty. The re-emerging Lithuanian state had not only to guarantee the preservation of national sovereignty, but also to create conditions favourable to radical legal and economic change. When considering the ways in which to reach these formidable goals, Lithuania has treated membership in NATO and EU as the means for the state's security. The process of access negotiations and then living up to the criteria for membership in these organizations led to a significant transformation of the state and the society. In regards to the security policy it led to the efforts of overcoming negative attitudes towards neighbouring states and accepting the idea of a collective security. In turn, this led to changes in the defence policy, replacing the idea of territorial defence to that of a collective defence and accordingly reforming the armed forces. Now a member of the EU and NATO, Lithuania has developed ambitions at becoming the leader of a region in spreading her experience of political and economic reforms to neighbouring eastern countries. Lithuania has supported the strengthening of the military dimension of EU, while being critical of the duplication of EU and NATO functions and capacities, and has linked her own security with the preservation of the strong transatlantic alliance.