The purpose of this article is to present factors determining the effectiveness of new investments in brown coal deposits. It discusses the weak and strong points of brown coal mining in Poland, as well as opportunities and risks in its development. The strong point is that Poland has abundant resources of lignite and the opportunity lies in the rising demand for energy. The weak point is that brown coal emits large amounts of CO2 and risk is perceived in that the EU tightens up its policy on coal-based production of energy. An analysis of all these factors allows reliable assessment of the discount rate on investment projects, which must be known for their profitability to be established.