National borders are often considered to constrain the international flow of products, services, people and capital. However, borders and differences between countries could also promote cross-border mobility. This contribution investigates what discourages and encourages cross-border shopping mobility. This is done by categorising differences between countries into more 'rational differences' on the one hand and more 'emotional differences' on the other hand. Furthermore, the 'bandwidth of unfamiliarity' concept is introduced to scrutinise how the interpretation by shoppers of both rational and emotional differences generates (im)mobility. In so doing, a 'border paradox' is discussed, where increasing cross-border integration (e.g. in the form of regional 'homogenisation') could coincide with decreasing cross-border mobility. This paradox is used here to reveal a possible flipside of the European Union policy to promote international mobility, by trying to dissolve borders between member states. Copyright (c) 2008 by the Royal Dutch Geographical Society KNAG.