Emotion reactivity refers to the extent to which one experiences emotion (Nock et al., 2008) and is an important underlying component of the development of effective social and behavioral functioning. Emotion reactivity can be understood as distinct from other emotion-related constructs because it is defined specifically as the speed and intensity of one’s initial and automatic emotional activation, as opposed to one’s ability to control or change one’s emotional response (Cole, Martin, & Dennis, 2004). Both over-reactivity and under-reactivity to emotional stimuli have been related to increased risk for psychopathological disorders such as major depressive disorder, social anxiety disorder, generalized anxiety disorder, and separation anxiety disorder (Bylsma, Morris, & Rottenberg, 2007; Goldin et al., 2009; Carthy, Horesh, Apter, Edge, & Gross 2010). A small and emerging literature indicates that neural markers signifying emotion reactivity to negative stimuli relate to patterns of risk for psychopathology in young children. However, far less is understood about how neural markers of emotion reactivity to pleasant stimuli, or the variability between neural markers of emotion reactivity to pleasant and unpleasant stimuli, relate to risk for psychopathology in children. It is also unclear whether the patterns of neural reactivity associated with processing unpleasant and pleasant stimuli are similar or different between young children and young adults. An understanding of similarities or differences of neural patterns of risk and reactivity between these age groups could provide important insights into the developmental differences in symptom patterns. Therefore, this study has two aims: 1) to determine whether neural markers of emotion reactivity to unpleasant and pleasant stimuli correspond to risk for psychopathology and how this relationship differs between young children and young adults and 2) to examine whether the time course of neural markers of emotion reactivity to unpleasant and pleasant stimuli relate to varied patterns of activation and whether they predict unique patterns of psychopathology symptomology.