The author presents an analysis of the modern state and main problems of the psychology of group decision-making on the basis of which he has worked out a complex strategy for studying group decision-making and obtained data revealing new regularities in the structural, functional and genetic organization of those processes. It has been proved that the processes of group decision-making are structurally organized and form a hierarchy comprising five basic levels. The author describes the principal regularities of the functional organization of group decision-making arguing that it belongs to a specific class of group processes - the integral group processes. The paper also discusses genetic regularities and main stages in the formation and development of group decision-making as well as its effect on group dynamics as a whole.