Gambling problems are experienced by about 1% of the adult population, with higher estimates reported in adolescents. Both positive and negative motivations for gambling exist and may contribute to gambling problems. Positive valence disturbances involving how people process rewards, including monetary rewards relevant to gambling, have been reported in gambling disorder and have been associated with the disorder and clinically relevant measures relating to impaired impulse control. Positive valence systems as they relate to gambling disorder and clinically relevant features thereof are considered in this chapter. Findings from neuroimaging data related to the positive valence system constructs of approach motivation, initial and sustained/longer term responsiveness to reward, habit and reward learning are reviewed. Possible interactions between positive valence systems and other Research Domain Criteria (RDoC) systems are also discussed within the context of gambling disorder, as is how the application of an RDoC framework can be used to further understanding of gambling disorder.