Objective: The purpose of this study was to find potential variables associated with the difference between subjective and object treatment responses in children with attention-deficit/hyperactivity disorder (ADHD) treated with OROS-methylphenidate (MPH).

Methods: We conducted a post-hoc analysis of data from a multicenter, open-label, 12 week trial of OROS-MPH in Korean children with ADHD. The subjective outcome measurement was the parent version of the ADHD Rating Scale-IV (ARS-P), and the objective outcome measurement was the Continuous Performance Test (CPT). We compared the children's demographic and disease-related variables among four groups, classified according to whether they showed subjective or objective improvement after MPH treatment.

Results: Higher baseline inattentive scores on the ARS-P were associated with a significantly higher probability of subjective treatment response among objective nonresponders (p=0.033). Lower baseline inattentive scores on the ARS-P were associated with a significantly higher probability of subjective nonresponse among objective responders (p=0.045). Lower baseline omission errors (p=0.006) and response time variability scores (p=0.011) on the CPT were associated with a significantly higher probability of both objective and subjective responses, compared with both types of nonresponse to treatment.

Conclusions: The baseline severity of parent-perceived inattentive symptoms was predictive of differences in subjective and objective treatment responses, and the baseline severity of neuropsychological deficit (inattention and inconsistency of attention) was predictive of responses, using both subjective and objective measurements.