Research over the last two decades on the role of positive emotions and cognitions in psychological functioning is leading to conceptual changes regarding the nature of mental disorders and the mechanisms underlying their onset and maintenance. This introduction to the latest breakthrough research on positive emotions and cognition offers a brief description of the emerging presence of positivity in current diagnostic systems like the DSM5 and Research Domain Criteria (RDoC). It also analyzes some select findings from the literature on experimental psychopathology supporting the relevance of examining positive aspects of functioning in clinical psychology. In addition, the study of positive aspects of psychological functioning adds a more conceptually complex understanding of psychopathology. The multiple perspectives encompassed in this special issue shed light on our understanding of the different roles that positive emotions and cognitions play in mediating normal and abnormal human functioning and their importance to improving research methods and interventions in psychopathology.