Aerosol nebulization is and most effective ways of treating airway diseases especially in children. Failure of inhaled asthma treatment is mainly due to inadequate deposition of drugs in the peripheral area of the lungs. The aim of this study was to compare the efficacy of a traditional mask and that of a new spacer mouth-mask (Nebula, Markos Mefar, Italy) when used with a jet nebulizer, by measuring aerosol deposition in the lungs, oropharynx, upper airways, and gastrointestinal tract. Twelve children without respiratory disease aged between 8 and 13 years were included in the study. Aerosol inhalation was performed using a jet nebulizer with 2 mL of saline solution containing 20 Mci of Tc99m-DTPA. The first group initially performed aerosol inhalation using a traditional facemask and then, one week later, using the new spacer mouth-mask. The second group performed aerosol inhalation using the new spacer mouth-mask first and then, one week later, using a traditional mask. Scintigraphic ventilation images were then obtained, and aerosol deposition in the trachea, oropharynx, lungs and stomach was measured. In the first group, the radioaerosol deposition in the peripheral lung area using the new spacer mouth-mask was greater 97.8 +/- 7.0 vs. 68.5 +/- 7.9 (p = 0.04). On the other hand, the oropharyngeal radioaerosol deposition was greater using the traditional mask: 50.2 +/- 5.2 vs 20.3 +/- 11.8 (p = 0.028). Similarly, in the second group the peripheral lung deposition was greater and the oropharyngeal deposition was less using the new spacer mouth-mask: 97.3 +/- 9.4 vs. 70.2 +/- 11.2 and 20.7 +/- 8.9 vs. 46.3 +/- 16.8 (p = 0.028 and 0.046 respectively). In conclusion, the new design of the spacer mouth-mask allows greater aerosol deposition in the peripheral lung area and less in other parts such as the oropharyngeal area, the central airways and the stomach.