AbstractAn essential component of many forest certification schemes is that landowners should voluntarily set aside a proportion of their forestland with the main aim of promoting biodiversity. However, the influence on biodiversity of such conservation areas is largely unknown. In this study, we compared the area extent, structural diversity of importance to biodiversity and stand characteristics between voluntary set-asides (VSA1Voluntary set-asides.1) established through certification, formally state-protected nature reserves (R2Reserves and national parks.2) and managed production forests (PF3Production forests.3). We used data from the Swedish National Forest Inventory and focused on forestry company land in boreal Sweden, amounting to about 7million ha. VSA and R were found to cover approximately the same area (0.6million ha each) but VSA were more numerous, especially for sizes 10,000ha belonged to R. VSA also occurred in more southerly locations. VSA were intermediate between R and PF regarding dead wood volume, number of large diameter trees ha−1 and value of a composite structural index. VSA had significantly higher volumes of the important broadleaved trees species aspen, rowan and sallow. VSA and R were much older and had lower site productivity than PF, but VSA had higher total standing volumes. Our analysis showed that certified-driven VSA are an important complement to traditional reserves regarding size and structural factors important to biodiversity. Thus, future development of planning models should consider both types of set-asides and their spatial configuration. This will require integration of non-state and state governance processes.