This study aimed to investigate factors correlated with dyspnea in cancer patients among a broad range of medico-psycho-social factors. A total of 171 consecutive outpatients with advanced lung cancer were recruited. Dyspnea was evaluated by using the Cancer Dyspnea Scale, a valid, reliable 12-item self-rating scale developed to assess the multidimensional nature of dyspnea in cancer patients. Possible correlates, including 1) medical (clinical stage, Performance Status, SpO(2), organic causes of dyspnea, other symptoms, such as cough and pain, etc.), 2) psychological (anxiety and depression), and 3) social (education, marital status, existence of confidants, etc.), factors were collected from medical charts, interviews, and self-rating questionnaires. Multiple regression analysis revealed that psychological distress, presence of organic causes, cough, and pain were significantly correlated with dyspnea (P < 0.05, multiple R(2) = 0.303). The present study confirms that dyspnea is multifactorial and that a beneficial therapeutic strategy might include intervention for psychological distress and pain.