In the fifty years since the publication of the Buchanan report, Regional Studies in Ireland, Ireland has transitioned from a rural to an urban society. Although a number of spatial plans have been introduced at regional and local levels, the growth of over 1.5 million people in the urban population has occurred in the absence of any strong national-level direction of spatial or settlement policy. This paper examines the nature of urbanisation in the half-century since 1966, by looking at the development of the urban hierarchy of cities and towns. Significant long-term changes in both the structure and the spatial expression of the urban hierarchy are identified, on the basis of which urbanisation is characterised as having been deconcentrated and decentralised. The paper identifies some implications of the observed shifts for contemporary policy concerns, and in particular the 2018 National Planning Framework.