Background <p>This study aimed to investigate the environmental factors associated with attention deficit hyperactivity disorder (ADHD) in Chinese children and adolescents with adiposity (obesity or overweight).</p> Methods <p>A total of 130 children and adolescents with adiposity and 130 age- and sex-matched controls with normal weight were enrolled in this cross-sectional study. Children with ADHD were identified based on International Classification of Diseases (ICD-10) codes. The severity for psychiatric and behavioral problems, ADHD symptoms, and oppositional defiant disorder was compared between the groups. Multivariable logistic regression analysis was performed to identify factors associated with the comorbidity of ADHD in children and adolescents with adiposity.</p> Results <p>The detection rate of ADHD was significantly higher in the adiposity group compared to control group (15.4% vs. 6.2%; <i>p</i> = 0.016). Children and adolescents with adiposity exhibiting higher scores in learning problems, impulsivity/hyperactivity, anxiety, and hyperactivity indices. Exploratory analyses indicated a positive correlation was found between BMI percentile (BMI-P) and inattention symptoms scores in individuals with ADHD (<i>r</i> = 0.512, <i>p</i> = 0.005). Logistic regression results showed that factors associated with ADHD in children and adolescents with adiposity included prolonged adiposity duration (&gt; 3 years) (OR = 5.61, 95% CI: 1.79–17.59, <i>p</i> = 0.003) and excessive screen time (&gt; 3&#xa0;h/day) (OR = 6.45, 95% CI: 1.59–26.11, <i>p</i> = 0.009).</p> Conclusions <p>Prolonged adiposity duration and excessive daily screen time were found to be associated with ADHD among children and adolescents with adiposity.</p>