The problem of research undertaken in the article concerns the adaptation of traditional models of calculating the cost of capital to the specifics of mining companies. Solutions known from the literature do not give reasonable results. This is due to the uniqueness of the activities of mining companies, in which case we are dealing with a lack of reference to the typical market situations. The aim of this article is to identify solutions that allow rational and reliable results to be obtained. One of the proposals is a modified Fama-French method. The article was tested by calculating the cost of capital in the largest Polish mining enterprises. The problem of calculation of the cost of capital is particularly important in the area of assessing the effectiveness of investment projects. The cost of capital is used as the discount rate in dynamic measures of performance, such as NPV.