en پژوهشي Original Research Article <p style="text-align: justify"><strong>Objective:</strong> The aim of the present research was to evaluate the psychological well-being and quality of sleep in addicts under methadone treatment for at least 6 months.</p> <p style="text-align: justify"><strong>Methods:</strong> A total of 40 individuals were selected through purposeful sampling method among the referring addicts to 2 addiction centers in eastern Tehran. Participants took the Ryff scale of psychological well-being (RSPWB) and Pittsburgh sleep quality index (PSQI).</p> <p style="text-align: justify"><strong>Results:</strong> Results of multivariate and univariate variance analysis demonstrated that addicts with more than 6 months of abstinence have significant difference in psychological well-being and quality of life (P&le0.01) compare to addicts with less than 6 months abstinence period.<br> There was also a significant relationship between sleep and its dimensions (P&le0.01).</p> <p style="text-align: justify"><strong>Conclusion:</strong> Addicts with abstinence period of more than 6 months have higher psychological well-being and better sleep quality than addicts with abstinence period of less than 6 months.</p> Addiction, Psychological well-Being, Quality of sleep 71 75 http://jpcp.uswr.ac.ir/browse.php?a_code=A-10-1-9&slc_lang=en&sid=1 Ebrahim Rezaei Dogaheh No Firozeh Jafari No Atousa Sadeghpour No Mohammad Ebrahim Maddahi No Shahab Mirzaei No Abbas Ali Hosseinkhanzadeh No Ali Reza Mohammadi Arya dr.mohammadiarya@uswr.ac.ir Yes Department of Preschool, University of Social Welfare & Rehabilitation Sciences, Tehran, Iran.