In this paper the most frequent personality disorders related to young adult cannabis-dependent treatment seekers are described. A sample of 141 cannabis-dependent patients was compared to 140 clinical patients with non-addictive disorders and to 140 normative subjects from the general population with the same demographic features (age, sex and socioeconomic level) to find out the prevalence of personality disorders. All subjects were assessed with the IPDE and the MCMI-II (for personality disorders) and with an interview for DSM-IV-R. According to the results, 32.8% of the clinical sample of cannabis-dependent patients and 23.7% of the general clinical sample (versus 10% of the normative sample) showed at least one personality disorder. The most prevalent ones were the narcissistic personality disorder (11.3%), followed by the antisocial and schizotypal personality disorder (9.9% each). Finally, implications of this study for clinical practice and future research in this field are discussed.