Abstract A gap model was developed for studying stand structure from the standpoint of biological diversity. In this model, stand structure is described by the diameter distribution of living and dead trees. The stage of decay and position of dead trees are also shown. The model output was compared with results from the literature representing sites in northern Europe, i.e. Finland, Sweden and Russian Karelia. The growth and structure of the pure pine stand were similar to those of measured stands, and the growth of spruce and birch stands were quite similar to that of the measured stands; but growth of alder and aspen stands deviated from that of measured stands. The growth and structure of a mixed stand were quite similar to the growth and structure of measured stands. Pure and mixed stands responded to management as would be expected based on the model. The model, which elaborately outlines how different forest management practices affect stand structure, can be used as a tool for research and decision making.