OBJECTIVE: To shed light on nebulized morphine, a new treatment for dyspnea in children with terminal lung disease. METHODS: A clinical case study was conducted on a patient in a tertiary care medical center. RESULTS: Nebulized morphine was administered in incremental doses ranging from 2.5 mg to 12.5 mg in a 10-year-old, 20-kg boy with end-stage cystic fibrosis. Before the nebulized morphine treatments were started, a dose of nebulized lidocaine failed to provide the patient with any relief. After each dose of morphine, the following parameters were recorded: visual analog "dyspnea" scores, vital signs, venous blood gases, and blood levels of morphine. The nebulized morphine was found to have a modest effect on the patient’s dyspnea, with no significant differences found between the varying doses. Venous carbon dioxide tension levels increased <4 mm Hg for all doses except 12.5 mg, for which there was a 9-mm Hg increase. Systemic blood levels of morphine were <10 ng/mL at all doses. The nebulized morphine did not cause any significant changes in blood pressure or heart rate for doses <12.5 mg. CONCLUSIONS: Inhaled morphine was associated with a mild, beneficial effect on dyspnea, with minimal differences found between the lowest and highest doses. This "ceiling" effect may be the result of saturation of opioid receptors in the lung, the variable bioavailability of inhaled morphine, or a placebo response. More studies are needed to determine what, if any, the optimum dose of nebulized morphine is for children.