Objective Subthreshold attention-deficit/hyperactivity disorder (ADHD) has been suggested to be a “morbid condition” which also needs medical attention. Methods The present study recruited 89 children with subthreshold ADHD (sADHD), 115 children with diagnosed ADHD (cADHD), and 79 healthy controls (HC) to explore the clinical manifestation, executive functions (EFs) of sADHD, and the caregiver strain. The clinical manifestation was evaluated through clinical interviews and parent-reports. Executive functions were assessed both experimen-tally and ecologically. Caregiver strain was measured by a parent-reported questionnaire. Results For the clinical manifestation, both sADHD and cADHD indicated impairments when compared with HC. The comorbidities and the scaled symptoms indicated that the externalizing behaviors were relatively less serious in sADHD than cADHD, whereas the in-ternalizing behaviors between two groups were comparable. For ecological EFs, sADHD scored between cADHD and HC in inhibition and working memory. For experimental EFs, sADHD was comparable to cADHD in inhibition, shifting, and was worse than cADHD in verbal working memory. For the caregiver strain, all scores of sADHD were between that in cADHD and that in HC. Conclusion Our present findings supported the suggestion of subthreshold ADHD as “morbid condition,” which should be treated with caution in clinical practice, especially for the internalizing behaviors and some key components of EFs.