Investigations indicate that there is an economic gain in being mobile in the Sound Region. The economic theory assumes that people are utility maximizers and should, in this case, be more mobile. The purpose of this dissertation is therefore to investigate the reasons for the immobility in the Sound Region and try to explain them with existing rationality theories. An empirical study is carried out in both Sweden and Denmark in order to reveal people’s reasoning about moving and commuting. Further the rationality theories are applied to the situation in the Sound Region and a model is constructed. At last it is concluded that the neo-classical theory fails to explain peoples’ behaviour while the three other theories can partly explain peoples’ behaviour and the reasons for mobility.