Decline of Atlantic white-cedar (Chamaecyparis thyoides), an uncommon, wetland tree of the eastern coastal United States, may be due in part to successional change in which cedar is replaced by more shade-tolerant tree species. The purpose of this study was to assess population structure and natural regeneration of cedar, project future changes in stand composition, and suggest appropriate management. The research was conducted at Brown Mill Pond, an ecological reserve in Rye, New Hampshire. Age and size structure of tree species were used to infer successional trends in five plant communities: (1) mixed conifer, (2) cedar I, (3) cedar II, (4) cedar-red maple, and (5) pond edge. Depth to water table was measured over two field seasons. Differences in species composition and stand structure were associated with variations in water table depth. In all communities except the pond edge and small (< 0.2 ha) patch cuts, cedar was even-aged (> 90 years old) and recruitment was lacking. In three communities over the next 100 years, abundance of arboreal associates will likely increase while cedar will decline. In a previously unreported successional sequence, eastern hemlock (Tsuga canadensis) and red spruce (Picea rubens) will likely become dominant in the mixed conifer community, which had the lowest water table. In areas with an intermediate water table, such as the cedar-red maple community, red maple (Acer rubrum) will achieve co-dominance with cedar. While cedar will likely decline in the absence of disturbance, it is unlikely that cedar will be completely replaced by arboreal associates at Brown Mill Pond as cedar establishment was evident along the pond edge and in small patch cuts.