Compact city is a concept of urban planning that is arguably a more sustainable urban design idea when compared to a sprawled structure, the existing diffusive model. Previous research has focused on the effectiveness of a hub city. However, the surrounding area, which primarily consists of suburban communities and agricultural lands, has not been adequately discussed. Therefore, this study examined two scales used in compact city policies (scale of the hub area and size of the population settling into the hub) to establish relationships between the scale, political costs and degree of isolation in the surrounding region.This study provided four overall findings ; 1) the larger the hub area and higher the population density of a hub area, the higher the political costs ; 2) degree of isolation for agricultural communities geographically distant from the city center is basically high ; 3) degree of isolation in suburban communities increases as the hub area and population density of the hub area rise ; and 4) a small scale hub area in terms of size of population settling into the hub impacts the relationships between political costs and degree of isolation in the surrounding region.