Sluggish cognitive tempo (SCT) symptoms have largely emerged from investigations of attention-deficit/hyperactivity disorder (ADHD). Recent research has demonstrated the relevance of SCT symptoms in the field of clinical child and adolescent psychiatry. The goal of this research was to study the symptoms of SCT in a clinical child and adolescent sample and to define its features and comorbid conditions. We reviewed 834 clinical records of patients referred to Child and Adolescent Mental Health Services and examined SCT symptoms and their relation with sociodemographic data, clinical diagnosis, comorbid conditions, Child Behavior Checklist dimensions, and intelligence quotient. Of the 515 patients (age range, 4 to 17 y, 62.5% male) for whom a fully completed Child Behavior Checklist for Children and Adolescents was available, 20.8% showed high levels of SCT symptoms. SCT symptoms were strongly associated with age, internalizing symptoms, learning disabilities, and ADHD inattentive subtype (ADHD-I). No significant correlations with intelligence quotient were found. We concluded that SCT symptoms are highly prevalent in a clinical sample, and that these symptoms might be related to the difficulties that some individuals have in responding to demands in their environments, such as academic or social demands, as they increase over time.