One of the main goals of stand structure modeling is choosing relevant laws to approximate tree distribution by diameter. The main inventory parameter of structural stand patterns is the tree distribution by diameter classes’ series. These data are used for compiling forest product tables, modeling classifications of forest and cutting area stock, study of stand growth, planning some forestry practices, etc. This study is devoted to the distribution of tree number and stock of Norway spruce (Picea excelsa) stands in Moscow Region. We used the data from the research carried out by Forest Inventory and Protection Department, MSFU, on 6 permanent trial plots starting from 1954 and also 10 trial plots with the size of 0.25 ha each were established in these stands. Grouping of trees according to natural diameter classes allowed us to compare the data about stock and tree number in stands of different ages. Distribution character of number and stock trees by natural diameter classes, was revealed in the given forest stands. Distribution of obtained empirical data permitted to develop laws of distribution. A number of distribution (d.) laws were used to adjust empirical data: normal d., lognormal d., exponential d., even d., gamma d., beta d., Waybull d., Maxwell d. and Ralay distribution. The check of a hypothesis about goodness of fit to the chosen law of distribution was performed using Коlmоgоrоv-Smirnov and χ2 and SPSS software. The results showed that beta law is the best fit for alignment of empirical data of tree number and stock for all ages. The results testify that with ageing asymmetry of tree number and stock the distribution from their symmetric distribution decreases. The estimation of reliability of asymmetry parameter by t-criterion shows that examined distributions are close to symmetric. Degree of kurtosis of empirical distributions decrease with ageing. The estimation of reliability of this parameter by t-criterion testifies the absence of deviation of
