Objective: This study examined the differences in the psychiatric comorbidity and suicidal behavioural aspects in accordance with the severity of Internet addiction in male adolescents.Methods: One hundred and twenty five adolescents from an Internet addiction rescue school and two middle and high schools in Seoul were enrolled for this study.The subjects were divided into a non-addict group, abuse group and dependence group according to a diagnostic interview by psychiatrists.Their psychiatric comorbidities and suicidal behavioural aspects were evaluated through a psychiatric clinical interview based on the Diagnostic and Statistical Manual of Mental Disorders, 4th edition, the Childrens Depression Inventory, the State-Trait Anxiety Inventory, Internet Addiction Test and a self-report questionnaire about behavioural aspects.Results: The psychiatric comorbidity distributions were significantly different in the abuse and dependence groups, particularly with the attention-deficit hyperactivity disorder and mood disorder items.The Childrens Depression Inventory, the State-Trait Anxiety Inventory, and Internet Addiction Test scores were also significantly different in the 3 groups.The Intemet Addiction Test, Childrens Depression Inventory, and State-Trait Anxiety Inventory scores correlated positively with each other.In particular, there were significant differences in the items regarding low self esteem, negative thought of the future and suicidal ideation between the abuse and dependence groups.Conclusion: This study suggests that there are differences in psychiatric comorbidity and suicidal behavioural aspects between adolescent male with Internet abuse and dependence.