Quality of Life (QOL) in opiate-addicted patients who are receiving methadone maintenance therapy is one of the important issues to be considered in the treatment of addiction. To determine a needs assessment using the PRECEDE model to find out factors related to QOL among Iranian male opiate addicts. This cross-sectional study was conducted in Kermanshah, Iran in 2013. A total of 762 male opiate addicts, who were referred to addiction treatment centers for receiving methadone maintenance treatment, were randomly selected to participate voluntarily in the study. SF-12, predisposing factors, enabling factors, reinforcement factors, and methadone maintenance treatment intention were used to find the related factors. Data were analyzed by the SPSS software (ver. 21.0) using the t-test, one-way analysis of variance (ANOVA), bivariate correlations, and linear regression at 95% significant level. Linear regression analysis showed the determinant variable accounted for 17% of the variation in QOL. Our findings suggest, providing social support for addicts could be beneficial results for the increasing quality of life among them.