Objectives: the present study explored the relationship between severity of psychiatric disorders and degree of opium dependence as a negative prognosis in treatment of drug addicts. Method: this study is a descriptive-cross sectional, the subjects were 240 (232 men and 8 women) randomly selected from among opium addicts seeking treatment. The instruments were an MMPI test and a psychiatric interview performed individually. The data were analyzed through a Chi Square, analysis of variance and a Tukey test. Findings: the most common method of using opium is the poker-stone method. The average drug taking period was 5.95 years. The average starting age was 24, and the average number of give-up attempts was 1.1. 50.4% were found to suffer from one or more psychiatric disorders, the most common ones being anti-social personality (25%), depression (20.5%) and anxiety (18.3%) respectively. The study demonstrated that psychiatric disorders intensify as opium dependence increases 30.5% of those who used opium smoking pipe, 39.2% of those who used poker and stone, 73% of those who sniffed the drug and 92.3% of heroine addicts were found to be suffering from psychiatric disorders. Results: the presence of mental disorders in addicts is not far from reality. To treat them, severity of addiction and psychiatric disorders should both be taken into consideration. Degree of addiction serves both as a sort of negative prognosis in unsuccessful give-up attempts, and as a cause for higher rates of comorbidity of psychiatric disorders.