Reforms to the judicial map were carried out recently in France and Belgium within the framework of a broader movement aimed at the modernization of the State. French and Belgian reforms shared a similar objective, namely to make judicial districts compatible with new public management methods. In both cases however, the government’s plans were met with hostility from magistrates, other justice professionals, and local officials. This comparative study suggests that the structures of the political and professional arenas and especially the institutional context and the degree of fragmentation of the decision-making process are the core factors determining the trajectories and results of judicial map reforms in France and Belgium.