The paper looks at the effects of employment concentration on resource allocation with a particular focus on one-company towns in Russia defined as towns where a single company accounts for a significant share of total employment of the locality. Empirical analysis of firms' production functions indicates that companies located in one-company towns are characterised by lower marginal product of labour, higher marginal product of capital and lower overall productivity pointing towards significant labour hoarding. One-company town enterprises are also found to be financially more vulnerable. The paper argues that the dominance of natural resources in the Russian economy and employment concentration is closely linked.