This study examined three kinds of social information-processing deficits in child psychiatric populations. The deficits studied were response decision biases, hostile attributional biases, and cue-utilization deficiencies. Subjects were diagnosed as hyperactive/aggressive (H/A) (n=24), exclusively hyperactive (n=14), exclusively aggressive (n=14), psychiatric control (n =23), and normal control (NC) (n=60) boys according to procedures suggested by Loney and Milich (1982). They were administered several tasks to solicit information-processing patterns. The H/A group was found to be deficient in all three areas asssessed, relative to the NC group. They were also deficient in response decisions and cue-utilization, relative to the other three groups of psychiatrically referred boys. Discriminant function analyses demonstrated that the H/A group displayed a distinct processing pattern. These results were found to be relevant to the study of behavior disorders, to social information processing theory, and to intervention efforts with these boys.