The value of any company can be estimated on the basis of application of three approaches: costing, comparative and profitable. Each of them has advantages and problems of using, yielding various results at an assessment of the companies in insufficiently developed, inefficient and inactive markets. Specifics of mining companies defines a choice of the integrated approach combining elements of costing and profitable approaches. The method of an assessment of value of mining companies on the basis of Olson's model is offered. The assessment of value of JSC Kovdorsky GOK is executed. Influence of the strategic investment project on a gain of value of the company is shown.