Since the second half of the twentieth century, the Brazilian government decided to steer the energy policy for the production of hydroelectricity, using as main argument the exceptional potential of the country in terms of water resources. With technical choices and important investments, Brazil has built hydroelectric plants/dams throughout its territory, favoring some specific areas (Southeast, Northeast and South), where the potential was higher. For decades, the country has experienced more or less intense phases of dams constructions, according to the national and international economic contexts. Nowadays, Brazil is at an intense construction stage. The construction of hydroelectric power plants (HPP) always entails a number of consequences, both positive and negative, besides covering a broad spectrum of society sectors: political, environmental, economic, planning, and social. In this article, we focus on the latter -the effects that the establishment of a hydroelectric plant causes on the people and their spaces, having as comparative point the experiences that occurred in the North and South of Brazil. What differences and similarities can be found in these regions? The social and spatial aspects involved in the dams impacts are considerable, which is why we will cover rural communities, looking at how they are destroyed, and sometimes, rebuilt.This article is an idea, an attempt of comparison, an exercise to be able to examine more thoroughly the spaces and thus evaluate the effects of dams. The idea of comparison is to control if generalizations are valid (28) ie, to verify or infer ideas, theories, and events between the South and the North. Comparisons are used to detail the entities, to provide data for explanatory theory (17). As explained by Sartori (28), "the compared survey does not have mathematical rigor, but allow identifying "trends laws"". The examples we cite reinforce and complement each other. The case studies are the cornerstones of the construction of theories and our comparison attempt may help to think of the spatial and social effects of dams.Our comparison is based on two different studies. The first, accomplished between 2006 and 2010 in southern Brazil in a doctoral research, was made up of three periods of field, six months each, around the river Uruguay. More than 150 questionnaires were completed, covering a little less than 580 people affected by two dams (Foz do Chapecó 1. PhD in Geography, Maine University (France); postdoctoral researcher at UNICAMP (Brazil). guillaume.leturcq@