To compare the therapeutic effects of two small-volume jet nebulization devices, a breath-actuated nebulizer (BAN) and a constant-flow nebulizer (CFN), this study was conducted. Seventy-two asthmatic patients, aged 5 to 15, were randomly enrolled into this study (39 to the CFN group, 33 to the BAN group). Nebulization treatment with terbutaline solution (5.0 mg /2 ml) diluted with 2 ml isotonic saline for 10 minutes was performed after measurements of baseline spirometry, SaO2, and pulse rate. Measurements of spirometry, SaO2 and pulse rate were repeated at 0, 5, 15 and 30 minutes after the end of the nebulization treatment. After treatment, for within-group comparison, all the spirometric parameters (including FEV1, PEF and FEF25-75%) and SaO2 at various time points of both groups significantly improved. The pulse rate also significantly increased (only at 15 and 30 min for the CFN group). For between-group comparison, the BAN group had greater improvement in all the data of spirometric parameters and SaO2 at various time points, but only reached statistical significance at some time points in PEF, FEF25-75% and SaO2. The pulse rate of the BAN group was significantly higher than that of the CFN group beginning 5 minutes after treatment. In conclusion, the BAN device is better than the CFN device in improving the spirometric parameters and oxygen saturation of asthmatic children during an equal 10-minute nebulization therapy. These results, associated with the higher pulse rate evoked in the BAN group, suggest a higher lung deposition ratio in the BAN device.