This paper sets out to provide evidence for the existence of spatial spillovers linked with the development of transport infrastructure. The author makes an attempt to measure the influence of both regional infrastructure (direct effect) and non-regional infrastructure (indirect effect) on gross value added generated in a region. In doing so, Rosik builds a bridge between the growth theory and the New Economic Geography concept. The author considers the case of Spain’s Galicia region in 1980-2000. The analysis makes use of the Cobb-Douglas production function, expanded to include transport infrastructure with the use of Spanish statistical data. The analysis confirmed the existence of negative spatial spillovers linked with infrastructure investment projects in this outlying district of Spain. The data shows that gross value added is positively correlated to the development of transport infrastructure in Galicia, but negatively correlated to the development of transport infrastructure in neighboring regions. The research findings confirm theoretical conclusions reached by economists linked with the so-called New Economic Geography theory to the effect that intraregional infrastructure has a positive influence on the development of outlying regions, while interregional infrastructure may lead to a deepening of regional disparities. This stems from the fact that, thanks to reduced transaction costs in interregional trade, companies are tempted to relocate their operations to more affluent regions. Rosik’s findings, supported by other empirical studies and theoretical discussions, are especially significant to Poland’s eastern regions, which are less developed than the rest of the country.