<p>Abstract</p> <p>Background</p> <p>Pain is said to be one of the most feared and distressing symptoms of cancer and one that disrupts all aspects of life. The purposes of this study were: 1) to compare depression and quality of life among Iranian cancer patients with and without pain; and 2) to determine the relationships between pain beliefs and depression and quality of life.</p> <p>Method</p> <p>A consecutive sample of gastrointestinal cancer patients attending to Tehran Cancer Institute were entered into the study. Three standard instruments were used to measure quality of life (the EORTC QLQ-C30), depression (the HADS) and pain beliefs (the PBPI).</p> <p>Results</p> <p>A total of 142 hospitalized gastrointestinal cancer patients, 98 with pain and 44 without pain were studied. The main findings of this study were that cancer patients with pain reported significantly lower levels of role functioning, emotional functioning and global quality of life. They also showed higher levels of depression than cancer patients who did not experience pain. Among patients with pain, higher scores on pain permanence and pain consistency were positively and significantly associated with higher depression. Also, higher scores on pain consistency were negatively and significantly associated with global quality of life.</p> <p>Conclusion</p> <p>This study has demonstrated the effect of cancer pain on patients' quality of life and emotional status and has supported the multidimensional notion of the cancer pain experience in cancer patients. Although these data are correlational, they provide additional support for a biopsychosocial model of chronic pain.</p