We present results from a cross-sectional study of the entire adolescent student population aged 14 to 18 years of the island of Kos, on the correlates between personality, illicit chemical substance use, and Internet abuse. Results demonstrate that adolescents who have used illicit substances and are abusing the Internet as well appear to share some common personality characteristics, namely those that are classified under the label of “psychoticism” in the Eysenck's personality model. An increase in the severity of pathological Internet use has been linked to increased chances of having used an illicit substance. Taking into account any common personality attributes, Internet addiction can still be useful as a predictor variable for substance use experiences. Future research should attempt to verify any biological common factors between chemical substances use and Internet abuse. Targeting the adolescent population that engages in increased Internet use may be of benefit for drug abuse prevention programs.