On the basis of Quay's (1988a, 1988b, 1993, 1997) model in which the Behavioral Inhibition System (BIS) and the Behavioral Activation System (BAS) are linked to various forms of child psychopathology, predictions were made regarding the relation between inhibitory control and two dimensions of psychopathology: externalizing and internalizing behavior. Inhibitory control was measured using two versions of Logan and Cowan's stop signal paradigm (1984; Logan, Cowan, & Davis, 1984; Osman, Kornblum, & Meyer, 1986, 1990). The primary outcome measure for the stop tasks was stop signal reaction time (SSRT) which measures the latency of the inhibition process. A positive relationship was predicted for externalizing behavior, whereas a negative relationship was predicted for internalizing behavior. A total of 42 non-clinical elementary school children, in the age range of 6 to 12 years, participated in the study. Externalizing behavior was positively related to response inhibition. Symptoms of ADHD seem to be better at predicting inhibitory functioning than symptoms of aggressive behavior disorders. Some support was found for a negative relation between internalizing behavior and inhibitory control. These findings support Quay's model and the discriminant validity of inhibitory control with regard to externalizing and internalizing behavior.