Background:
Drug dependence disorder patients are strongly associated with a high rate of smoking. Hospitalization aiming to drug abstinence will increase chance of quitting successfully. Moreover, smoking cessation intervention providing during hospitalization will also associated with the increased rate of long-term abstinence from any drug abuse.

Methods:
This quasi-experimental research aimed to examine the effects of promoting smoking cessation program in drug dependence disorder patients at the national institute on drug abuse treatment in southern Thailand applying the Social Cognitive Theory. The samples comprised of 23 current smokers with drug dependence who were admitted at rehabilitation unit, at the institute. This program was conducted over a period of 8 weeks and composed of 6 activities including self-observation, judgment process, self-reaction, motivation, individual counseling and assigned the smoke-free environments in accordance with the laws. Data were collected by interviews at pre and post intervention on the 4th and 8th week. Statistics analysis was performed by using descriptive statistics and inferential statistics, i.e., Paired Sample t-test, Cochran's Q test and Friedman test.

Results:
The results showed that the samples had significantly higher mean scores of perceived self-efficacy to quit smoking and outcome expectation of smoking cessation at post intervention on the 4^th week (p < 0.05). In addition, 5 in 23 current smokers (21.7%) and 9 in 23 current smokers (39.1%) were able to quit smoking, at post intervention on the 4th and 8th week, respectively.

Conclusions:
The smoking cessation program can help smokers with drug dependence to stop smoking so it should further apply to any similar health service facilities.