Magnitude estimation (ME) of inspiratory resistive (R) loads has been studied in asthmatic children. Some children have been reported to be unable to perform the perception task. One reason some children may be unable to perform the ME task is Attention Defi cit Disorder (ADD) or Attention Deficit Hyperactivity Disorder (ADHD). The aim of this study was to determine if asthmatic patients with ADD/ADHD have a perceptual and/or attention deficit in the ME of graded inspiratory R loads.Methods: Asthmatic children aged 11–18 years were classified into ADD/ADHD and asthma control groups. Perception of extrinsic loads was assessed by handgrip ME of inspiratory R loads. A methacholine challenge was performed and the PC20 for each subject determined.Results: There was no significant difference between asthma control and ADD/ADHD groups in the group mean for the slope of ME-R load slopes. The ADD/ADHD subjects had significantly greater variability in ME of R loads.Conclusions: Asthmatic children with ADD/ADHD do not have an impaired perception of extrinsic respiratory loads but do have difficulty attending to the perceptual task. Difficulties in their asthma management may be due to their attention deficit and not their symptom perception.