Two processes have been identified as governing decoy and compromise effects in decision making: The value shift process suggests that the decoy influences the cognitive evaluation of the target or the competitor in terms of their perceived attribute values. The value added process postulates that the decoy provides an increment in value for the target because the presence of the decoy helps justify the choice of the target over the competitor. Several theories for explaining such value shifts are analyzed and then tested in an experimental setting. The results are surprising and contradict traditional assumptions, since a negative value shift is established for the target relative to the competitor. Furthermore, there are clear indications that value shift and value added processes operate simultaneously and may compensate for one another. © 2009 Wiley Periodicals, Inc.