en سوء مصرف و وابستگي به مواد Substance abuse and dependence كاربردي Applicable <p style="text-align: justify;"><strong>Objective:</strong> This study aimed to investigate the effect of psychotherapy based on quality of&nbsp;life improvement (QoLI) on emotion regulation and the prevention of relapse in addicts under&nbsp;methadone maintenance therapy (MMT).<br> <strong>Methods: </strong>This research is a semi-experimental pretest-posttest study with a control group.&nbsp;Eight sessions of psychotherapy training based on QoLI were implemented for the experimental&nbsp;group; the control group received no intervention. We used difficulties in emotion regulation&nbsp;scale (DERS) to evaluate the participants. In the post-test phase, both control and experimental&nbsp;groups had a urine test for morphine. For data analysis, SPSS version 18 and the statistical&nbsp;methods of analysis of covariance and Chi-square test were used.<br> <strong>Results:</strong> There is a significant difference between the scores of the difficulties in emotion&nbsp;regulation between experimental and control groups in post-test (P˂0.05). Moreover, the rate&nbsp;of relapse among participants in the experimental group was significantly lower than that in&nbsp;the control group.<br> <strong>Conclusion:</strong> Psychotherapy based on QoLI was effective on the reduction of difficulties in&nbsp;emotion regulation and prevention of drug abuse relapse among addicts under MMT.</p> Addiction, quality of life therapy, difficulties in emotion regulation, relapse, methadone maintenance therapy. 25 32 http://jpcp.uswr.ac.ir/browse.php?a_code=A-10-318-1&slc_lang=en&sid=1 Sajjad Motahhari sajad_motahari67@yahoo.com@yahoo.com Yes Department of Counseling, Faculty of Psychology and Educational Sciences, Allameh Tabataba’i University, Tehran, Iran. Ahmad Etemadi No Department of Counseling, Faculty of Psychology and Educational Sciences, Allameh Tabataba’i University, Tehran, Iran. Abdollah Shafiabady No Department of Counseling, Faculty of Psychology and Educational Sciences, Allameh Tabataba’i University, Tehran, Iran. Milad Qorbani Vanajemi No Department of Counseling, Faculty of Psychology and Educational Sciences, University of Tehran, Tehran, Iran.