OBJECTIVE This study aims to identify environmental risk factors associated with behavioral problems in children and adolescents with attention deficit hyperactivity disorder (ADHD). METHODS A case-control study was conducted in children aged 4-15 years comprising 92 children diagnosed with ADHD and 92 controls without ADHD. Stratified sampling was used to select 184 participants residing in Chiang Mai and Lamphun provinces, Thailand. Data were collected from the mothers of the participants using a self-report questionnaire between May and August 2022. The questionnaire consisted of three parts: child characteristics (gender, age, underlying diseases, past illness history), mother’s characteristics (age, income, occupational status, history of cigarette smoking and alcohol drinking), and maternal perceptions about caring for the child and the child’s behavioral problems (exposure to chemicals/toxicants, frequent punishment, excessive use of digital media and games). Data were analyzed using descriptive statistics, chi-squared test, odds ratio (OR) and logistic regression using SPSS version 21. RESULTS Most of participants were males (86.96%) while 13.04% were females. The results showed that the ADHD cases were significantly more likely than the controls to have underlying diseases such as G6PD, allergy, and asthma (p = 0.006). There was also a statistically significant correlation with smoking history in the mothers of ADHD cases (OR = 2.64; 95% CI: 1.36-5.13 p = 0.004). In terms of maternal perceptions, the mothers of ADHD children were significantly more likely than the controls to have frequently punished the child (OR = 6.26; 95% CI: 3.24-12.07; p < 0.001), to have children who were exposed to chemicals (pesticides and fertilizer) or toxicants (passive smoking) (OR = 4.14; 95%CI: 1.76-9.73; p = 0.001), and to have allowed their child to use digital media and play video games excessively (OR = 2.82; 95% CI: 1.55-5.16; p = 0.001). After adjustment for other environmental risk factors, frequent child punishment (ORadj = 4.32; 95% CI: 2.13-8.78; p < 0.001) and exposure of the child to chemicals/toxicants (ORadj = 2.66; 95% CI: 1.00-7.02; p = 0.049) were found to be significantly related with ADHD. CONCLUSIONS Frequent child punishment was the most significant environmental risk factor related to behavioral problems among children with ADHD. This indicates the importance of healthcare providers developing strategies and/or interventions to enhance knowledge and awareness in mothers of ADHD which can improve treatment outcomes. KEYWORDS ADHD, risk factors, behavioral problems, maternal percep- tions