Attention-deficit/hyperactivity disorder (ADHD) has been found to be highly comorbid in children and adolescents with obsessive-compulsive disorder (OCD). Some have proposed, however, that obsessive anxiety may cause inattention and executive dysfunction, leading to inappropriate ADHD diagnoses in those with OCD. If this were the case, these symptoms would be expected to decrease following successful OCD treatment. The present study tested this hypothesis and evaluated whether ADHD symptoms at baseline predicted OCD treatment response. Obsessive-compulsive and ADHD symptoms were assessed in 50 youth enrolled in a randomized controlled trial investigating selective serotonin reuptake inhibitor and cognitive behavioral treatment. Repeated-measures analysis of variance (RMANOVA) revealed that ADHD symptoms at baseline do not significantly predict treatment outcome. A multivariate RMANOVA found that OCD treatment response moderated change in inattention; participants who showed greater reduction in OCD severity experienced greater reduction in ADHD-inattentive symptoms, while those with less substantial reduction in obsessions and compulsions showed less change. These findings suggest that children and adolescents with OCD and inattention may experience meaningful improvements in attention problems following OCD treatment. Thus, in many youth with OCD, inattention may be inherently tied to obsessions and compulsions. Clinicians may consider addressing OCD in treatment before targeting inattentive-type ADHD.