In recent years, city-regional development has received increasing attention from the media, policymakers as well as the academic spheres but yet ‘city-region’ remains a relatively understudied subject in Vietnamese literature. Contemporary works have appealed to how city-regions are functional economic areas, but the development of Vietnamese city-regions has been rather normative and politically guided. More empirical works are much needed so that city-regional policies are more evidence-backed and, therefore ultimately, more effective. With particular scope into the delineation of city-regional boundary, this paper contributes to that growing body of literature in two ways: (1) to provide an overview of methodology to define boundaries of polarized regions - of which city-region is a special form - and (2) to present an original attempt to empirically delineate city-regional boundary in Vietnam, with ‘Can Tho City-region’ as a case study. The article is both empirical and experimental which, the author hopes, would ignite further interest in this growing field.