IntroductionRecent works in economics have attempted to show the influence of information and communication technologies (ICT), which are usually used to store and transfer data, not only on the organisation and performances of firms, but also on their location. Although it is generally accepted that an efficient use of ICT is dependent on the organisation of the firm, the analysis of their spatial impacts has resulted in contradictory conclusions. Some authors support the hypothesis that the diffusion of ICT is likely to modify the geography of the firms' locations by facilitating long-distance communications. Thus, contradictory locational tendencies, expressing different spatial logics, are evidenced (Cornford et al, 2000). On the one hand, by facilitating coordination within and between firms, ICT are thought to provide more independence in location choices. This could give rise to spatial reorganisations of firms, leading to the phenomenon of a spatial decentralisation of activities:``the new telecommunication technologies facilitate the decentralization and relocation of industrial and administrative establishments, especially for those where the rapid acquisition of information and knowledge is not essential'' (Thisse and van Ypersele, 1999, page 24). On the other hand, ICT could reinforce the tendency towards industrial concentration: thanks to the fall in the costs related to geographical distance, firms could decide to set up in highly industrialised areas in order to take advantage of complementarities and externalities (Ellison and Glaeser, 1997). Other authors bring to the fore the view that ICT have no influence by emphasising the irreducible character of local interactions, particularly in the case of activities which mobilise or necessitate complex knowledge combinations (Lung et al, 1997;Storper, 1996).