The purpose of the study was to investigate the underlying structure and dimensionality of dispositional optimism as measured by the Life Orientation Test (LOT). Whereas the LOT was originally developed to measure a unidimensional construct, several studies have suggested a bidimensional underlying structure (i.e., separate optimism and pessimism factors). Data were collected among adolescents in Norway (total N = 2,239). Support was found for a hierarchical factor model comprising optimism and pessimism as first-order factors and ‘life orientation’ as a second-order factor. Additionally, some empirical support for an unfolding tendency was found, implying that the bidimensionality typically found in several studies is partly due to a method artifact. In conclusion, a unidimensional conceptualization of dispositional optimism was supported.