Statement of problem: Index of orthodontic treatment need (IOTN) has several applications and advantages for determination of orthodontic treatment need. Due to the effects of different factors such as gender, age and socio-economic status on treatment need based on self evaluation, it is important to evaluate correlation between orthodontic treatment need assessed by self- evaluation and real treatment need assessed by IOTN.Purpose: The purpose of this study was to evaluate the correlation between orthodontic treatment need as assessed by IOTN and self- evaluation in 18-22 year old patients.Materials and Method: Of 18-22 year old patients referred to Shiraz dental clinics, 240 were selected by random cluster sampling method. IOTN and self- evaluation questionnaires were filled in. In self- evaluation questionnaire, the mean scales for all the questions were determined as the scale of patient. The correlation between treatment need as assessed by IOTN and self- evaluation was evaluated by Pearson correlation and Partial correlation statistical analysis.Results: There was a significant moderately positive correlation between Dental Health Component (DHC) and self- evaluation (r=0.51). Also, the correlation between Aesthetic Component (AC) assessed by the examiner and patient and self evaluation was significantly positive. (r=0.39, r=0.31)Conclusion: The significantly positive correlation between IOTN and self- evaluation indicates that in assessment of orthodontic treatment need, not only standard indices but also self- evaluation of the patient should be taken into account.Key words: Index of Orthodontic Treatment Need (IOTN), Self-evaluation, Correlation