Objective: In this study we aimed to assess the aggression and trait anger-anger expression levels in parents of children with attention deficit and hyperactivity disorder (ADHD) and to investigate the relationship between symptoms of ADHD/oppositional defiant disorder and aggression and anger levels of parents. Methods: The study sample consisted parents of 58 children diagnosed with ADHD between 6-14 ages. The healthy control group consisted of 54 healthy children's parents. Both ADHD and healthy group were assessed with Sociodemographic Data Form, Buss-Perry Aggression Questionnaire and Trait Anger Expression Inventory. Symptoms of ADHD in children were evaluated with the DSM-IV Based Behavior Disorders Screening and Rating Scale. Results: We found that trait anger level of mothers was higher in ADHD group than the control group. Anger control scores of ADHD parents was lower than the control group. Buss-Perry Aggression Questionnaire total aggression score and hostility sub-scale score was found to be higher In ADHD group than healthy control group. Additionally, attention deficit and oppositional defiant symptom levels of ADHD children were in relation with hostility level of parents and trait anger level of mothers. Conclusion: In our study trait anger and total aggression levels of mothers were found to be higher in ADHD group than healthy control group. Anger control levels of parents of ADHD group were lower than the control group. Parents of children with ADHD should be aware of their emotion and behavior related to anger and aggression during the treatment of child.