Background: Factors requiring midazolam in addition to systemic opioids to control dyspnea in cancer patients have yet to be evaluated. Methods: We retrospectively analyzed data for cancer patients who received systemic opioids to relieve dyspnea from April 2019 to July 2021 in Wakayama Medical University Hospital, Japan. Patients were divided into an opioid-alone group and an opioid plus midazolam group, according to the treatment of dyspnea. Results: The total of 107 patients included 85 patients (79.4%) in the opioid alone group and 22 patients (20.6%) in the opioid plus midazolam group. Age<60 years (p=0.004) and male sex (p=0.034) was significantly associated with the addition of midazolam. Multivariate analysis found age <60 years (OR=5.34, 95%CI: 1.66–17.21; p=0.005) was associated with the addition of midazolam. Conclusion: Age <60 years is factor requiring midazolam in addition to systemic opioids to control dyspnea in cancer patients.