This paper analyses the theoretical concept of sustainable development and different points of view to it. A generalized point of view based on ecological, social and economic groups is presented. Principles of sustainable development, forms of sustainability are discussed. Sustainable conception's influence on tourism is analyzed Sustainable tourism is discussed as region's opportunity to create infrastructure of tourism where natural resources would be kept and market, similar to competition in tourism market, would be created at the same time. Sustainable tourism conception and principles, that highlight peculiarities of sustainable tourism conception as compared to general sustainable conception, are presented. Sustainable tourism conception is created considering the factors governing Lithuanian region's tourism competition. The paper aims at representing sustainable conception and principles and applying them to tourism, discussing assumptions of adjusting competition and sustainable tourism development in Lithuanian tourism service. Research tasks are as follows: to analyze progress of conception of sustainable development and forming consistency and to define the levels of sustainable development; to present basic forms of sustainable conception and to define them; to form sustainable tourism system and to highlight the basic principles of sustainable tourism development and the influence on tourism system; to present interactive relationship between sustainable tourism and tourism competition, and their influence on tourism; to evaluate the possibilities of applying sustainable tourism development in Lithuanian tourism service.