The conception of investment activity is discussed in this article. The main factors in investment decision making are considered a lot of elements of investment activity are examined, such as: investment strategy investment decision, investment design, the investment medium and subjects of investment activity. The investment strategy is defined as a system of investment activity long run goals and the selection of the most efficient ways for their achievement. The investment activity determined the opportunities for improvement of results such as profit-making and own assets increasing. The investment decision depend on lot of factors, such as type of investment; investment project value, multiplicity within the capacity of projects; the insufficiency of financial resources, the risk of making an incorrect decision. The investment design represents the development of technical documentation package including a feasibility report. The investment cycle has three phases: preliminary, investment and production. As an investment medium maybe: creating and reconstruction of fixed capital; securities and bank deposit; scientific and technical products, property right and intellectual property right. The subjects of investment activity: investors, executors of works; users of object, providers, financial intermediaries, foreign natural and juridical person, organs of government and international organs.