An international Sluggish Cognitive Tempo (SCT) Work Group proposed a new term for SCT, “cognitive disengagement syndrome,” that more accurately describes the syndrome than does SCT. According to the Work Group, symptoms of SCT represent a cognitive dimension (cognitive disengagement) and a motor dimension (hypoactivity). Our study determined (1) if distinct factors representing cognitive disengagement and hypoactivity emerged when SCT items were factor analyzed and (2) the degree of differences in cognitive disengagement and hypoactivity within diagnostic groups. Mothers rated 1,177 children with autism, 725 with ADHD-Combined, and 307 with ADHD-Inattentive (4–17 years) and 665 elementary school children (6–12 years) on the Pediatric Behavior Scale (PBS). SCT prevalence rates were autism 32%, ADHD-Inattentive 27%, ADHD-Combined 18%, and elementary school students 7%. Factor analysis of the SCT items yielded two factors reflecting cognitive disengagement (in a fog/confused and stares/preoccupied/in own world) and hypoactivity (sluggish/slow moving/low energy, drowsy/sleepy/not alert, and tires easily) in all diagnostic groups. Cognitive disengagement prevalence rates and scores were significantly higher than hypoactivity in the autism and ADHD-C groups and in the autism and ADHD-C subgroups of children with SCT (but not in the ADHD-I and elementary school total groups and SCT subgroups). Our findings factor analyzing five SCT items support two SCT subfactors: cognitive disengagement and hypoactivity.