This study was designed to investigate the effects of guided imagery on depression, serum cortisol level and imagery ability of psychiatric patients. The subjects were assigned to the control(N=17) and experimental(N=17) groups. These two groups received both pre-test and post-test. There were no significant differences between these groups in terms of their age, frequency of admission, days of hospitalization, depression, serum cortisol level, imagery ability etc. The experimental group participated in the guided imagery for 19 minutes per at one given time, conducted twice a week during 4 weeks period. The data were analyzed after using the unpaired t-test, paired t-test and x^2-test. The results were as follows : 1. There was a significant difference in depression between the groups. The depression scores decreased significantly after the treatment in the experimental group. 2. Serum cortisol level decreased significantly after the treatment in the experimental group. 3. There was a significant difference in imagery ability between the two groups. The imagery ability scores increased significantly after the treatment in the experimental group. In conclusion, the guided imagery was effective in reducing the depression and serum cortisol level, in improving the imagery ability. So the researchers suggest that guided imagery be used as an independent nursing intervention in the clinical practice.