Recently, there has been an increasing level of interest in subscores for their potential diagnostic value. Haberman (2008) suggested a method based on classical test theory to determine whether subscores have added value over total scores. This paper provides a literature review and reports when subscores were found to have added value for several operational data sets. Then this paper provides results from a detailed simulation study that examines what properties subscores should possess in order to have added value. The results indicate that subscores have to satisfy strict standards of reliability and correlation to have added value. Augmented subscores (Haberman, 2008; Wainer et al., 2001) were found to have added value more often.