Background and objectives: Attention-Deficit/Hyperactivity Disorder (ADHD) symptoms and other mental health problems appear early in life and proper treatment is essential for a positive long-term outcome. The present study examines the level of agreement, and potential gender differences, between parents’ and teachers’ reports of ADHD symptoms and other mental health problems in 305 Greek children aged between 6-9 years. Methods: Parents and teachers of 147 boys and 158 girls attending the first three grades of 10 primary schools in the wider area of Northern Greece completed the Strength and Difficulties Questionnaire (SDQ- Goodman, 1997) and the Child Attention Profile (CAP-Barkley, 1990). Results: The level of agreement between parents’ and teachers’ reports was low to moderate for the SDQ (0.16-0.34) and satisfactory for the CAP (0.60-0.66). Parents reported more hyperactivity, emotional, and conduct problems than teachers according to SDQ and more overactivity and attention-deficit with hyperactivity according to CAP. Gender differences in ratings were found as well, since boys were reported as being more hyperactive according to SDQ and as having more overactivity and attention-deficit with hyperactivity according to CAP than girls. Conclusions: Findings are discussed in terms of the importance of using multiple informants to gather data on disruptive behaviour through rating scales.