This paper presents an analysis of urban spatial structure and its trends in the OECD between 2001 and 2011. It does so by using a standardised definition of urban areas in 29 OECD countries as composed of high density cores and their respective commuting zones. While urban population is growing everywhere, the way in which populations locate throughout the urban space differs across OECD cities and countries. The prevalent trend is an increasing dispersion of the population, with growth taking place outside existing centres. However, in specific countries, there are cities experiencing a higher growth in their central cores, while others are strengthening their polycentric structures. Overall, the population has grown more in relatively low-density locations close to the main centre, but outside it. Closeness to sub-centres also proves to be a strong advantage for growth and suggests the emergence of new centralities shaping urban spatial structures.