Evidence on the association between somatic chronic diseases in ID-adolescents and the full range of pervasive developmental disorder behavior (PDD behavior) is scarce. The aim of the present study is to assess the association between somatic chronic diseases in ID-adolescents and mild PDD behavior. We obtained data on 1044 ID-adolescents, aged 12-18, attending secondary schools in the Netherlands. Parents of the adolescents completed the Dutch version of the Children's Social Behavior Questionnaire (CSBQ) parent version, covering a wide range of PDD behavior, and questions about chronic diseases and background characteristics of their child. ID-adolescents with somatic chronic diseases showed more PDD behavior, in particular milder forms, than their peers without chronic diseases. In addition, ID-adolescents with somatic chronic diseases in combination with pervasive development disorders (PDD) and attention deficit hyperactivity disorder (ADHD) also showed more PDD behavior than their peers with only PDD/ADHD. Clinicians should be extra alert on PDD behavior, in particular the milder forms, in ID-adolescents when somatic chronic diseases are present. However, to strengthen our results about the relationship between somatic chronic diseases in ID-adolescents and PDD behavior studies are needed using both the CSBQ and standardized diagnostic instruments. (Contains 3 tables.)