The article deals with the problem of assessing economic diversification at the level of individual federal subjects. Diversification is one of the strategic goals for development of Siberia. Assessing the progress in furthering this goal requires its consideration at the level of measurable indicators. In world practice, measurement and evaluation of the level of diversification of the regional economy are based on a variety of indicators reflecting individual characteristics of diversification processes. This paper presents a comparative analysis of diversification in subjects of the Siberian Federal District over the period of 2008–2013. In assessing diversification, we used the Herfindahl–Hirschman indices (gross value added and number of employees by economic activity, the structure of shipped products in manufacturing, the export commodity structure) and the proportion of manufacturing, share of single-industry towns resident in the regional population, and the number of small businesses (enterprises) per 10000 people. Discrepancies in the estimates of various indicators and contradictory trends are shown in the development of diversification processes in individual subjects of the Siberian Federal District. Correlation analysis showed no strong relationship between diversification and the growth rate of the regional economy or the existence of a strong link between economic diversification and its stability. The regions are grouped according to the level of their stability.