Aim: The aim of this study was to identify the main symptoms of psychotic disorders, especially schizophrenia, major depression and bipolar mood disorder. Method: Using a retrospective design, 204 inpatients diagnosed with psychotic disorder (84 schizophrenics, 52 major depressions and 68 bipolars) in Fatemi and Eisar hospitals in city of Ardabil were selected. They underwent Semi- Structured Interview of Rating Scale for Psychotic Symptoms (SSCI-RSPS). The data were analyzed using factor analyzes, and discriminate analyzes. Results: There were four major factors, including somatic hallucination, delusion of having ultra sensory powers, disturbed action due to thought and auditory hallucination explaining %11.8, %8.7, %5.5, and %5.3 of the variance respectively. Five factors were extracted in the schizophrenia group: perception disorder of the environment, somatic hallucination, religious ultra sensory delusion, disturbed action due to thought and auditory hallucination explaining %10.47, %7.72, %6.29, %6.28, and %6.26 of the variance respectively. Five factors were extracted in bipolar mood disorder, including omnipotence, auditory hallucination, illusion, vestibular motor hallucination and distractibility, explaining %25, %11.38, %8.2, %6.5, and %5.4 of the variance respectively. In the major depressive disorder group %27, %11.9, %8.9, %6.5, %5.8, %5.6, %5.2 of the variance were explained by seven mood non-congruent delusions: jealous delusion, nonverbal auditory hallucinations, illusion, somatic hallucination, distractibility, magic thought, and erotic delusion. Conclusion: In accordance of the findings 63.2% of disorders can be correctly classified by RSPS.