In Wallonia, economic activity zones started to be created since just after the Second World War and have always contributed to both economic development and good regional planning. Originally reserved for large-scale industries of the fordist type, the formula was extended to include small and medium-sized companies, except retail business, and even generated specialised spaces like science parks, multi-modal transport centres and business parks. Throughout its development the success of the zones and the parks has scarcely weakened: there are over 200s in the region today in which over 4,500 companies can be found, totalling over 20% of private employment in Wallonia. Those companies correspond to the large majority of the new industries and activities of the heavy service sector, as well as to a very large number of transfers of activities that were, long ago, located in the urban towns. Nevertheless, the recent expansion of these zones raises an increasing number of questions: should their expansion be encouraged or should it instead be slowed by more efficient management? This article studies these questions and suggests avenues for reflections and suggestions that cross the divide between the zones themselves and, more globally, the planning and development policies.