Within a given historical event, the International Expositions (also called World Fairs), two Brazilian s pavilions projects by architect Lucio Costa were selected for study, to the Philadelphia World Fair in 1926 and the New York World Fair in 1939, both in the United States. The analysis of the cultural context, the conformation of the architectural competition and finally the composition of the projects aims to connect the issue of national representation - program-specific of exposition pavilions - with the Brazilian architecture s discourse development in two different periods of its 20th century s history: the neo-colonial and modern period. As projects of the same architect, who has established himself as one of the greatest representatives of the profession in Brazil, the study is done in order to understand the formation of both his design practice, contemplating the appropriation of traditional forms of a colonial past, as well as his theoretical discourse, understanding art and technique in contemporary thought.