This experimental research was designed to evaluate the effects of promoting patients participation in self-care on symptom distress mood state and self-care deficit based on Orems nursing theory. Fifty-four hospitalized cancer patients, receiving chemotherapy at Ramathibodi Hospital were selected by purposive sampling and randomly assigned to either control (n=27) or experimental group (n=27) Subjects in both groups received usual care provided by nurses in the setting but the experimental group received additional supportive-educative nursing system provide by the Investigator. Mood state and Symptom distress were measured by LASA Scale (Sutherland Walker & Till 1988) and Modified Symptom Distress Scale (Holmes 1989). Self-care deficit was measured by the Self-Care Deficit Assessment Form derived from the Self-Care Deficit Related to Nausea and Vomiting Assessment Form and the Rosenbergs Self-Esteem Scale. The latter was used to measure self-esteem which was a part of self-care deficit assessment. The results of the study indicated that subjects in the experimental group had significant lower mean score of symptom distress only on the second post chemotherapy day and significant lower mean score on self-care deficit on the first, second and third post chemotherapy day than patients in the control group (p<0.05 p<0.01, respectively) but there were no statistically significant difference between the two groups on mood state on the first three post chemotherapy days (p>0.05). The findings supported the vapidity of Orems nursing theory that explained nurses and patients should act together to allocate the role of each in development of patients self-care capabilities. This study was limited. Its implications for clinical practices and education must be defined. Further study is recommended.