The development of plant communities spatial structure in the course of primary succession was studied in abandoned gravel and sand quarries in the forest tundra of Northwest Siberia (Labytnangi town area). The sand and gravel pits have «medium» environmental conditions, because they are not influenced by glacial water and have no toxic ground contrary to other traditional subjects of primary succession study (recently deglaciated terrain, volcanic lava, open mine spoils etc.), so the pits can be considered as a proper analogous model to understand the fundamentals of plant cover development on primary surfaces within the extension landscape. In 1998, in plant communities at different stages of primary succession, the vertical and horizontal structure of plant cover were fixed as 61 designs made on plots 0.5 2 m. The quarries vegetation has 1 to 4 layers, but most of them are sparse or fragmentary. Plant community stratification during primary succession goes gradually and depends on upper shrubs layer and/or ground mosses layer development. Thus, woody plants settlement on primary surfaces and their growth rate are important for stratification process. According to our data of long-term vegetation dynamics monitoring (1995-2005) on 25 permanent plots, shrubs occur in the communities first, trees occur next, and dwarf shrubs are the last. The total number of woody plants reaches maximum by 10-11 years after starting of the natural recovery, and does not change up to 30-40 years (the oldest quarries studied). Horizontal plant distribution patterns were analyzed on the base of 61 obtained designs, and 3 main types of the patterns were distinguished. These types («punctatum»-from the Latin púnctum, «rotundatum»-from the Latin rotúndus, «ambitatum»-from the Latin ámbitus) differ from each other by plant individuals distribution. As a rule, all 3 types form various mix combinations in the studied communities. An original classification of the spatial structure of plant communities developing during primary succession is made with account of the vertical stratification and horizontal pattern of the cover. Our results demonstrate that although vertical and horizontal differentiations of vegetation cover go simultaneously, the vertical stratification is faster than horizontal pattern development and the layers in plant community form earlier than the stable path mosaic typical to undisturbed forest tundra vegetation.