This study sought to evaluate the construct validity of schizoid personality disorder (SZPD) by investigating a sample of 2,619 patients from the Norwegian Network of Personality-Focused Treatment Programs by a variety of statistical techniques. Nineteen patients (0.7%) reached the diagnostic threshold of SZPD. Results from the factor analyses indicated that SZPD consists of three factors: social detachment, withdrawal, and restricted affectivity/ anhedonia. Overall, internal consistency and diagnostic efficiency were poor and best for the criteria that belong to the social detachment factor. These findings pose serious questions about the clinical utility of SZPD as a diagnostic category. On the other hand, the three factors were in concordance with findings from previous studies and with the trait model for personality disorders in DSM-5, supporting the validity of SZPD as a dimensional construct. The authors recommend that SZPD should be deleted as a diagnostic category in future editions of DSM-5.