Dual task performance in children with Tourette Syndrome (TS) was studied. The participants were children with TS (N = 48, 40 male, 8 female), Attention Deficit Hyperactivity Disorder (ADHD; mixed types N = 44, 34 male, 10 female) and unaffected controls (N = 48, 34 male, 14 female). Eleven of the TS participants had no comorbidities (TS only) and they were compared to matched groups of participants with TS plus comorbidities (TS+), ADHD, and controls. Each participant was administered screening measures of behaviour, intelligence and verbal ability, as well as specific tests of dual task performance. Children with TS-only correctly recalled fewer digit span forward trials, and identified fewer spaceship pairs than controls under single task conditions in the SkySearch subtest of the Test of Everyday Attention for Children. However, the TS-only and control groups showed better counting performance while simultaneously searching for targets, than the TS+ and ADHD groups. Taken together, these results suggest that some previously reported cognitive deficits in children with TS are due to comorbidities, rather than to the syndrome itself.