Objective: Children with attention-deficit/hyperactivity disorder (ADHD) often have sleep complaints and also higher rates of psychiatric comorbidities such as mood and anxiety disorders that may affect sleep. The authors hypothesized that children with ADHD and psychiatric comorbidities would have higher overall sleep disturbance scores as measured by a sleep questionnaire than children with ADHD without comorbidities. Methods: This cross-sectional analysis in an academic center studied 317 children with ADHD; 195 subjects had no comorbid conditions, 60 were anxious and 62 were depressed. Participants completed the Schedule for Affective Disorders and Schizophrenia for School-Age Children–Present State, 4th Revised Edition and the Children's Sleep Habits Questionnaire. Results: Median age (range) was 8.9 (6–18.7) years; 78% were male. Median (interquartile range) Total Sleep Disturbance Score (TSDS) on Children's Sleep Habits Questionnaire for subjects with no comorbidities was 44 (40–49); anxiety, 48 (43–54); and depression, 46 (41–52). Compared with subjects without comorbidities, TSDS in anxious subjects was greater (p = .008). TSDS in depressed subjects was not significantly different. Compared with subjects without comorbidities, anxious subjects had higher Bedtime Resistance, Sleep Onset Delay, and Night Wakings subscales (p = .03, .007, and .007, respectively); depressed subjects had higher Sleep Onset Delay and Sleep Duration subscales (p = .003 and .01, respectively). Conclusions: Anxiety in children with ADHD contributed to higher overall sleep disturbance scores, compared with children with ADHD alone. Both comorbidities were associated with higher Sleep Onset Latency subscale scores. Further study of the impact of psychiatric comorbidities on sleep in children with ADHD is warranted.