en Psychiatry Psychiatry Original Research Original Research <p> <strong> Background </strong>:Co-morbid psychiatric disorders affect prognosis, psychosocial adjustment and post-surgery satisfaction in patients with gender identity disorder. In this paper, we assessed the frequency of personality disorders in Iranian GID patients. </p><p> <strong> Methods </strong>: Seventy- three patients requesting sex reassignment surgery (SRS) were recruited for this cross- sectional study. Of the participants, 57.5% were biologically male and 42.5% were biologically female. They were assessed through the Millon Clinical Multiaxial Inventory II (MCMI- II). </p><p> <strong> Results </strong>: The frequency of personality disorders was 81.4%. The most frequent personality disorder was narcissistic personality disorder (57.1%) and the least was borderline personality disorder. The average number of diagnoses was 3.00 per patient. </p><p> <strong> Conclusion </strong>: The findings of this study revealed that the prevalence of personality disorders was higher among the participants, and the most frequent personality disorder was narcissistic personality disorder (57.1%), and borderline personality disorder was less common among the studied patients. </p> Personality disorder, Gender identity disorder. 582 587 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1-722&slc_lang=en&sid=1 Azadeh Mazaheri Meybodi mazaheri.azadeh@yahoo.com 200319475328460013235 200319475328460013235 No Shahid- Beheshti University of Medical Sciences, Tehran, Iran. Ahmad Hajebi hajebi.ahmad@gmail.com 200319475328460013236 200319475328460013236 No Mental Health Research Center, Iran University of Medical Sciences,Tehran, Iran. Atefeh Ghanbari Jolfaei draghj@yahoo.com 200319475328460013237 200319475328460013237 Yes Minimally Invasive Surgery Research Center, Iran University of Medical Sciences, Tehran, Iran.