Purpose <p>Opioids are recommended as first-line pharmacological therapy for cancer dyspnea. However, real-world opioid prescribing practices, including early dose adjustment for patients with impaired organ function, remain unclear. The purpose of this study was to clarify the real-world selection of opioid type and dosage adjustment for cancer-related dyspnea in opioid naïve patients, particularly in those with renal and liver dysfunction.</p> Methods <p>A secondary analysis of a multicenter observational study carried out at 12 palliative care facilities across Japan. The subjects were 224 hospitalized adult cancer patients who were opioid naïve and initiated regular systemic opioid therapy for dyspnea. The types of opioids (morphine, oxycodone, hydromorphone, fentanyl) and their dosages (oral morphine equivalent daily dose (OMEDD)) were collected from the initiation (T0) to 72&#xa0;h later (T3).</p> Results <p>Morphine was the most frequently selected (132/224, 58.9%), followed by oxycodone (51/224, 22.8%), hydromorphone (30/224, 13.4%), and fentanyl (11/224, 4.9%). Mean OMEDD at T0 and T3 were 15.7 ± 7.7&#xa0;mg and 20.0 ± 9.7mg for the morphine group, 14.1 ± 4.4&#xa0;mg and 20.9 ± 10.7mg for oxycodone, 10.9 ± 3.0&#xa0;mg and 15.8 ± 5.5mg for hydromorphone, and 18.5 ± 5.4&#xa0;mg and 15.8 ± 7.0mg for fentanyl. In patients with renal dysfunction, oxycodone was the most frequently selected (15/26, 57.7%), and its dosage was increased over time, while the dosage of morphine and fentanyl was stable. In patients with liver dysfunction, morphine was the most frequently selected (12/24, 50.0%), with no significant dosage increases observed for all opioids.</p> Conclusion <p>Morphine was the most frequently selected opioids for dyspnea in patients with cancer. Over the initial 72-h period, opioid dosages increased by 25–50% for most opioids. In patients with renal or liver dysfunction, opioid selection and dosage adjustments reflected clinical considerations of organ function.</p>