Stand structure, often quantified using the percent canopy cover associated with various structural layers, is an important characteristic used when modeling ecosystem diversity and function. A model is presented, PERCOVE, that classifies individual trees in a stand into structural layers using user-defined rules, models the spatial arrangement of trees, creates a map showing tree crowns, and uses the map to compute an estimate of the percent canopy cover associated with the structural layer. The model, interfaced with the Forest Vegetation Simulator (FVS), can be used to evaluate the structure of existing stands represented by inventory data and stands projected using FVS.