Objective: To investigate adult ADHD symptoms and satisfaction with life, with a focus on age and sex differences. Method: This study is based on parents in the Norwegian Mother and Child Cohort Study (MoBa). The Adult Self-Report Scale (ASRS-6) and Satisfaction With Life Scale (SWLS) scores were analyzed from 33,210 men and 41,983 women from young to middle adulthood. Results: Mean ASRS total score was significantly higher in men, where 5.1% scored above cutoff, compared with 2.9% in women. Factor loadings supported the two ASRS subscales: Inattention (Inatt) and Hyperactivity-Impulsivity (HyImp) in both sexes. A significant decline with age was found on HyImp, whereas Inatt scores were reasonably stable in men and u-curved in women. High ASRS scores were associated with lower SWLS, but poor satisfaction with life was found only in high-scoring women. Conclusion: Our findings suggest caution to age and sex when using the ASRS-6.