||Purpose:Autonomic nervous system (ANS) functioning has been widely studied in relation to antisocial beha-vior, such as Conduct Disorder (CD). However, research in females is scarce andfindings are inconsistent. Thisstudy investigated baseline ANS activity in CD children and adolescents and tested for sex differences.Furthermore, subgroups of CD were investigated: +/?Limited Prosocial Emotions (LPE), +/?comorbid inter-nalizing disorders (INT).Methods:Baseline ANS activity was measured by Heart Rate (HR), Heart Rate Variability (HRV; parasympatheticactivity), Pre-Ejection Period (PEP; sympathetic activity), and Respiration Rate (RR). 659 females (296 CD, 363controls) and 351 males (187 CD, 164 controls), aged 9–18 years participated.Results:Baseline HR, HRV and PEP did not differ between CD subjects and controls in both sexes. RR was higherin CD participants than controls amongst females, but not males. LPE was unrelated to ANS activity, whereasfemales with CD + INT presented lower HRV.Conclusions:These results suggest that baseline ANS activity is not a robust indicator for CD. However, deviantANS activity–especially parasympathetic activity - was observed in CD females with internalizing comorbidity.