Attention deficit/hyperactivity disorder (ADHD) and tic disorders (TD) commonly co-occur. Clarifying the psychiatric comorbidities, executive functions and social adjustment difficulties in children and adolescents of ADHD with and without TD is informative to understand the developmental psychopathology and to identify their specific clinical needs. This matched case-control study compared three groups (n=40 each) of youths aged between 8 and 16 years: ADHD with co-occurring TD (ADHD + TD), ADHD without TD (ADHD - TD) and typically developing community controls. Both ADHD groups had more co-occurring oppositional defiant disorder than the control group, and the presence of TD was associated with more anxiety disorders. TD did not impose additional executive function impairments or social adjustment difficulties on ADHD. Interestingly, for youths with ADHD, the presence of TD was associated with less interpersonal difficulties at school, compared to those without TD. The potential various directions of effects from co-occurring TD should be carefully evaluated and investigated for youths with ADHD. (Contains 4 tables.)