The Reinforcement Sensitivity Theory proposed three neuropsychological systems which mediate individual differences in emotion, motivation and learning: Behavioral Activation System, Behavioral Inhibition System and Fight/Flight System, which involve reward, punishment and threat sensitivity systems, respectively. The systems´ sensitivity mediates individual differences on the personality traits Impulsivity and Anxiety. One of the most widely used scales to detect and measure individual differences in these systems is the Sensitivity to Punishment and Sensitivity to Reward Questionnaire. This thesis includes five studies with which we evaluate variance in the structural and functional brain according to the individual differences in Gray´s proposed systems´ sensitivity. Thus, the first two studies analyzed the relation between gray matter volume and the individual differences in the Sensitivity to Reward and Punishment subscales included in the aforementioned questionnaire. Sensitivity to Reward was inversely associated with gray matter volume in the dorsal striatum. Conversely, Sensitivity to Punishment was directly related to gray matter volume in the left amygdale and hippocampus. Furthermore, three functional studies analyzed brain activation associated with individual differences on Sensitivity to Reward scale. The first study showed that brain activity during appetitive emotional picture processing was associated with Sensitivity to Reward in the mesial prefrontal cortex and the adjacent rostral cingulate, while brain activation in the hippocampus/parahippocampus during aversive emotional picture processing was inversely related to Sensitivity to Reward. The second study revealed that Sensitivity to Reward was directly related to the mesial prefrontal cortex and dorsal striatum, and inversely related to the right inferior prefrontal gyrus during the inhibitory control in approach-avoidance conflicts. The third study demonstrated that Sensitivity to Reward during cognitive and emotional interference tasks was related to brain activation in the rostral anterior cingulate during cognitive and emotional Stroop tasks. However, dorsolateral prefrontal cortex activation was directly related to Sensitivity to Reward during cognitive interference, and amygdale activation was inversely related to this variable during emotional interference. Briefly, individual differences in brain structure and function may be associated with system-related personality traits according to the Reinforcement Sensitivity Theory.