To describe the associations between a range of baseline factors (demographic, family and clinical) and parent-reported health-related quality of life (HRQoL) of children with ADHD taking part in the ADORE study. HRQoL was rated using the Parent Report Form of the Child Health and Illness Profile-Child Edition (CHIP-CE). Forward-stepwise linear regression models were used to investigate associations with 26 independent variables. Separate models were fitted for each of the five CHIP-CE domains (Satisfaction, Comfort, Resilience, Risk Avoidance and Achievement) and two subdomains of Achievement (Academic Performance and Peer Relations). CHIP-CE domain mean scores were lower than community norms, especially for Risk Avoidance and Achievement, indicating a low level of HRQoL. Clinical factors significantly associated with a poorer HRQoL included ADHD symptoms (inattention, hyperactivity-impulsivity), conduct problems, peer relationship problems, having asthma, multiple other somatic symptoms and co-ordination problems. Family factors, such as having a parent with a health or mental health problem possibly caused by the child's illness, child not living with both parents and maternal smoking during pregnancy were also associated with a worse HRQoL in some CHIP-CE domains/subdomains. Numerous factors independently impact on the HRQoL of children with ADHD.