Background: Many psychiatric patients have nicotine and other substance dependence. Objective: To determine the prevalence of nicotine and opium dependence among psychiatric in-patients inKerman, a city in southwesternIran. Methods: Three groups of psychiatric inpatients, chronic medical patients and a sample from local population, each including 400 subjects were selected. Nicotine dependence was evaluated by Fagerstrom test for nicotine dependence. Scores >7 were considered positive for nicotine dependence. Opium dependence was evaluated by a semi-structured interview based on DSM IV. Results: 115 (28.75%) out of 400 psychiatric patients had nicotine dependence which was significantly higher than that of the two other groups (p<0.0001). 140 (35%) of psychiatric patients had opium dependence that did not differ from chronic medical patient but was higher than the control group (p<0.0001). Frequencies of nicotine and opium dependence were higher among males in all three groups. The highest frequencies of nicotine and opium dependence were observed among patients with post-traumatic stress disorder. Conclusion: Psychiatric patients are predisposed to substance dependence. One plausible reason for opium dependence in our patients is cultural factors. Substance dependence associated with other psychiatric disorders should be considered whenever treatment plan is made.