Attention Deficit-Hyperactivity Disorder (ADHD) is one of the most prevalent psychiatric disorders in childhood and adolescence, often accompanied by comorbid disorders. A high standard of diagnostic assessment combined with a demand for valid diagnostic instruments is necessary. The K-SADS-PL is an established semi-structured interview, focusing on the categorical assessment of psychiatric disorders. The aim of the following study was to examine specific characteristics of ADHD symptomatology including functional and behavioral assessment. Therefore correlations between the result in a diagnostic interview (K-SADS-PL) and different ADHD-specific instruments were performed. Groups were formed (exposed vs. unexposed), based on the diagnostic finding in the K-SADS-PL. Group-specific test score differences were calculated and compared by multivariate analyses of covariance. Children with ADHD showed a significantly higher impact of conduct and emotional problems than the unexposed group. Health related quality of life was more impaired in children and families suffering from ADHD which refers to the relevance of family-oriented psychotherapy.