Deadwood, whether expressed in volume, diversity or continuity, is nowadays widely acknowledged as being an important component of forest ecosystems, and has therefore been addressed in most recent studies dealing with forest conservation and management. However, and despite the growing use of the concept of naturalness in the management plans of French forest reserves, the dynamics of deadwood remains greatly unknown in West European temperate forests. In this context, and in order to answer a growing demand arising from the managers of forest reserves, a specific long-term monitoring scheme has been implemented in all main forest habitats since its launch in 2005. Our talk will present some preliminary results of this country-wide monitoring based on data from 36 Biological Reserves and 18 National Nature Reserves. In this network, a comprehensive data set of living and dead tree measurements has already been collected on >5.000 permanent plots covering a wide range of situations. Although most of the sites showed significant amounts of deadwood (mean: 38.1 m3/ha), we will focus our presentation on the important differences that were found between sites and within sites. We analyze the relationships between these differences and habitat types, altitude and management practices. Future surveys will allow us to better understand the driving forces behind these differences and will provide us with management tools to assess how these values will/can increase in the future.