Capital cities form the focus of a sub-field in urban studies. Much of the literature concerning their planning concentrates on their histories, and on the core precincts in which these cities of power often focus their governmental functions. Lacunae in the capital city literature include little attention to twenty-first century capital city settings in large, complex and expanding city-regions; to recent developments in broader urban literatures/city studies; and to contemporary directions of their planning and emergent futures. This article seeks to contribute to filling these gaps through a comparative study of five national capital city-regions on four continents: those of Delhi, Beijing, Paris, Pretoria and Brasília. The methods applied rest on secondary sources as well as some primary research in each of these city-regions. The article proceeds through a substantial review of literatures on capital cities and relevant urban studies, and sets out a general comparison of the five city-regions historically and in terms of their current features. We then proceed to an examination of present challenges and planning approaches in each city-region in turn. A discursive conclusion explores possibilities for the future and argues that by ‘catching up’ conceptually to contemporary trends, including debates around ‘extended urbanisation’, capital city studies, as a sub-field of urban scholarship, could play a useful role in promoting critique of policy and planning responses.