OBJECTIVE: To investigate inflations (initial sustained inflations and consecutive inflations) and breathing during mask ventilation in preterm infants at birth. STUDY DESIGN: Resuscitation of infants 15 mL/kg in sustained inflations, >10 mL/kg in consecutive inflations), and airway obstruction. RESULTS: In 27 infants, we analyzed 1643 inflations, 110 breaths in between inflations, 133 breaths coinciding with an inflation, and 1676 breaths on continuous positive airway pressure. A large mask leak frequently resulted in low V(Te). Breathing during positive pressure ventilation occurred in 24 of 27 infants (89 ). Median (IQR) V(Te) of inflations, breaths in between inflations, and breaths coinciding with an inflation were 0.8 mL/kg (0.0-5.6 mL/kg), 2.8 mL/kg (0.7-4.6 mL/kg), and 3.9 mL/kg (0.0-7.7 mL/kg) during sustained inflations and 3.7 mL/kg (1.4-6.7 mL/kg), 3.3 mL/kg (2.1-6.6 mL/kg), and 4.6 mL/kg (2.1-7.8 mL/kg) during consecutive inflations, respectively. The V(Te) of breaths were significantly lower than the V(Te) of inflations or breaths coinciding with an inflation. CONCLUSIONS: We often observed large leak and low V(Te), especially during sustained inflations. Most preterm infants breathe when receiving mask ventilation and this probably contributed to the stabilization of the infants after birth.