Depressed individuals show impaired performance in tests of attention and concentration. They also exhibit PET resting state abnormalities in dorsal prefrontal cortex and anterior cingulate, regions known to be substrates of attentional processing in healthy individuals. This chapter outlines a strategy to study neuropsychological mechanisms in emotional disorders using functional imaging methods. It reviews evidence strongly implicating the dorsolateral prefrontal cortex, particularly in the right hemisphere, as a key brain structure in emotion/cognition interactions in negative mood states. It will be argued that this neocortical region is a crucial convergence zone, being the substrate of sustained attention to the external environment, and the main target of limbic-cortical influences during changes in mood state across health and disease.