OBJECTIVE: To describe the prevalence and gender characteristics of mental health problems in extremely preterm/extremely low birth weight (EP/ELBW) children without intellectual disabilities, blindness, deafness, or severe cerebral palsy compared with a reference group at 11 years of age. METHODS: In a national cohort of EP/ELBW children, mental health was assessed by parental and teacher report by using the Autism Spectrum Screening Questionnaire, the Swanson, Noland, and Pelham Questionnaire IV (attention-deficit/hyperactivity disorder), the Screen for Child Anxiety Related Emotional Disorders, symptoms of obsessive-compulsive disorder (OCD), and a total difficulties score from the Strength and Difficulties Questionnaire. Pervasive rating was defined as both parent and teacher scoring the child >/=95th percentile (>/=90th percentile for total difficulties score) of the reference group, which was the population-based Bergen Child Study. RESULTS: Of eligible children, 216 (64%) EP/ELBW and 1882 (61%) reference children participated. EP/ELBW children were at significantly increased risk of pervasive rated symptoms of autism (odds ratio 4.3, 95% confidence interval 2.0-9.3), inattention (8.3, 4.4-15), anxiety (2.3, 1.4-3.7), OCD (2.6, 1.4-3.7), and >/=90th percentile for total difficulties score (4.9, 2.9-8.2). Reported by either parents or teachers, 54% of the EP/ELBW and 21% of the reference children had >/=1 mental health problem (odds ratio 4.5, 95% confidence interval 3.3-6.1). There were no significant interactions between EP/ELBW and gender in mental health outcomes. CONCLUSIONS: EP/ELBW children without severe disabilities had increased risk of symptoms of autism, inattention, anxiety, and OCD. Gender differences were comparable to the reference group.