Youths with extreme obesity (Body mass index (BMI)>40) are at increased risk for physical and mental health impairments but this patient group has received little attention in research. This study aimed to analyze the pain experience and mental health impairments of youths with extreme obesity compared to those with mild and moderate obesity (BMI=30-39.9) by considering gender differences. Cross-sectional data of 431 youths (M=16.6; SD=2.3; 53.1% female) were analyzed. Of these, 159 (36.8%) youths were characterized by extreme obesity. Self-reported sociodemographic data, pain-related variables, depression, and health-related quality of life (HRQoL) were assessed with standardized questionnaires. Data were analyzed with univariate tests and logistic regression models. Youths with extreme obesity reported more pain in the last 4 weeks (p=.018), increased pain-related impairments in daily life (p=.009), more pain-related days of absence (p=.030), higher depression scores (p = .030), and reduced HRQoL (p=.005) compared to youths with mild and moderate obesity. In regression models, extreme obesity and pain in the last 4 weeks were associated when additionally including sex and age in the model (odds ratio 1.88; 95 % confidence interval 1.16 - 30.40, p=.010). In the subgroup of extreme obesity (n=159), women (n=83) reported more pain in the last 4 weeks (p=.001), higher depression scores (p<.001), and lower HRQoL (p<.001) compared to men (n=76). These findings underpin the need for standardized assessments of pain and mental health, especially in the treatment of female youths with extreme obesity. Upcoming studies may analyze reciprocal interactions since both aspects are important barriers for lifestyle changes and weight loss.