Background: Previous studies have found considerable overlap between attention/hyperactivity problems, aggressive/oppositional problems and delinquent/conduct problems in adolescents. Sampling and Methods: Mothers of 1,965 11- to 18-year-olds (1,116 boys, 849 girls), referred to mental health agencies, completed the Child Behavior Checklist (CBCL). Latent class analysis was conducted on the Attention Problems scale (representing problems with attention, impulsivity and hyperactivity), Aggressive Behavior and Rule-Breaking Behavior scales of the CBCL. Results: Six latent classes were found. One of these classes contained individuals who suffered predominantly from attention problems and to a far lesser degree from aggressive or rule-breaking behaviors. The other 5 classes represented individuals with varying degrees of attention problems, aggressive behaviors and rule-breaking behaviors. Conclusions: Contrary to previous studies, the present study indicated that, in a large referred sample, problems with attention, impulsivity and hyperactivity can be considered as a diagnostic construct that should be distinguished from aggressive or rule-breaking behaviors. However, the present study did not support the existence of diagnostic classes constituted by individuals who primarily suffer from aggressive behaviors or rule-breaking behaviors, and not from attention problems or hyperactivity. Implications of these findings for future research and clinical practice are discussed. The value of the study was limited by the use of parent reports only. Copyright © 2007 S. Karger AG.