This study examined the relation between internalizing and externalizing symptoms in two groups of prepubertal boys (with and without multiple chronic tic disorder) with diagnosed attention-deficit hyperactivity disorder (ADHD). Parents and teachers completed the Child Behavior Checklist (CBCL) and Teacher's Report Form (TRF), respectively. Children were carefully evaluated for the absence of a chronic tic disorder. Boys with ADHD and chronic multiple tic disorder (ADHD/+tics) received significantly higher (p= .0032, Bonferroni correction) scores for the Anxious/Depressed, Thought Problems, and Attention Problem scales of the CBCL and the Delinquent Behavior, Thought Problems, and Somatic Complaints scales of the TRF than did boys without chronic tic disorder (ADHD/−tics). Although many of the individual items that differentiated (p< .05) the two groups of boys pertained to behaviors that characterize motor tics, obsessions, or compulsions, the ADHD/+tics group exhibited higher rates of anxious behavior (CBCL) and obscene language (TRF) than did the ADHD/−tics group. Anxiety/depressive symptoms were associated with aggressive/oppositional behavior in both samples. Children with mild tic disorder were more similar (CBCL) to ADHD/−tics boys than they were to children with more severe tic disorder. The relatively higher rate of comorbidity in the ADHD/+tics group suggests that tics may be a marker for more severe symptomatology in clinic-referred samples of children with ADHD. Furthermore, these data suggest that it is not the presence, per se, but rather the severity of tic disorder that is associated with higher rates of emotional and behavioral disturbances.