Background: Health-related quality of life (HR-QoL) stands as a ă determinant ``patient-related outcome'' and correlates with ă cardio-pulmonary exercise test (CPET) in adults with chronic heart ă failure or with a congenital heart disease (CHD). No such correlation ă has been established in pediatric cardiology. ă Methods and results: 202 CHD children aged 8 to 18 performed a CPET ă (treadmill n = 96, cycle-ergometer n = 106). CHD severity was stratified ă into 4 groups. All children and parents filled out the Kidscreen HR-QoL ă questionnaire. Peak VO2, anaerobic threshold (AT), and oxygen pulse ă followed a downward significant trend with increasing CHD severity and ă conversely for VE/VCO2 slope. Self-reported and parent-reported physical ă well-being HR-QoL scores correlated with peak VO2 (respectively r = ă 0.27, p < 0.0001 and r = 0.43, p < 0.0001), percentage of predicted peak ă VO2 (r = 0.28, p = 0.0001 and r = 0.41, p < 0.0001), and percentage of ă predicted VO2 at AT (r = 0.22, p < 0.01 and r = 0.31, p < 0.0001). ă Significant correlations were also observed between several HR-QoL ă dimensions and dead space to tidal volume ratio (VD/VT), oxygen uptake ă efficiency slope (OUES), oxygen pulse but never with VE/VCO2 slope. The ă strongest correlations were observed in the treadmill group, especially ă between peak VO2 and physical well-being for parents (r = 0.57, p < ă 0.0001) and self (r = 0.40, p < 0.0001) reported HR-QoL. ă Conclusions: Peak VO2 and AT are the two CPET variables that best ă correlated with HR-QoL in this large pediatric cohort, parents' reports ă being more accurate. If HR-QoL is involved as a ``PRO'' in a pediatric ă cardiology clinical trial, we suggest using parents related physical ă well-being HR-QoL scores. (C) 2015 Elsevier Ireland Ltd. All rights ă reserved.