This article discusses the three Finnish city names Helsinki, Espoo, and Vantaa, and the urban discourses that surround them. The study reveals patterns of socio-spatial differentiation by examining what meanings people attach to these capital region cities and investigating how these meanings are expressed in online discourses. Using the methodological approach of corpus-assisted onomastics (CAO), this study incorporates onomastics, geographical information systems (GIS), and corpus linguistics. This interdisciplinary research also examines how corpus-assisted discourse studies (CADS) and GIS can be combined to reveal and visualize the contextual information and discursive patterns of toponyms. For this investigation, a data set of 2.7 billion words was collected from the Suomi24 Corpus, one of the biggest discussion fora in Finland. The use of social media corpus as a data source increases the authenticity of this research, as the data was not collected specifically for this study. The analysis reveals that the most frequent digital discourses about the cities refer to places and directions, housing, and mobility. The occurrences differ quantitatively and qualitatively between each city. This paper paves the way for future onomastic studies to research actual name usage using this new methodology. Knowledge gained from such research may not only enrich the field of onomastics, but also facilitate more socially sustainable urban planning.