As software development continues to increase in complexity, involving far-reaching consequences, there is a need for decision support to improve the decision making process in requirements engineering (RE) activities. This research begins with a detailed investigation of the complexity of decision making during RE activities on organizational, product and project levels. Secondly, it presents a conceptual model which describes the RE decision making environment in terms of stakeholders, information requirements, decision types and business objectives. The purpose of this model is to facilitate the development of decision support systems in RE and to help further structure and analyse the decision making process in RE.