<p>Based on the study of scientific literature, the article reveals the ambiguity of interpretation of the concept “cost of capital” and shows the shortcomings of existing methods for determining the amount of cost of capital and discounting cash flows. An approach, developed by the authors to determine the value of the cost of capital and discounted cash flows in assessing the effectiveness of investment projects, is proposed for use in Uzbekistan and other countries with an insufficient level of stock market development.</p>