OBJECTIVES: Our objectives were to characterize resident knowledge of bag-mask ventilation (BMV) and to identify predictors of a well-developed mental model of BMV. METHODS: A pilot survey of airway experts identified 6 steps considered essential in situations of difficult BMV. Subsequently, residents from pediatric, emergency medicine, and medicine-pediatric programs at a tertiary care hospital completed the same pediatric scenario-based item given to airway experts. RESULTS: Of all surveys, 75% (n = 103) were completed. No resident identified all 6 maneuvers for difficult BMV. With decreasing frequency, the items identified were as follows: reposition patient/airway (82%), oral airway (61%), nasal airway (39%), jaw thrust (37%), 2-person technique (7%), and call for help (4%). Emergency medicine residents had a higher mean (SD) score than the medicine-pediatric and pediatric residents of a possible 6 (2.71 (1.26) vs 2.01 (1.07), P = 0.004) and were significantly more likely to identify certain maneuvers: oral airway (81% vs 52%, P = 0.006), nasal airway (57% vs 29%, P = 0.006), and 2-person technique (14% vs 3%, P = 0.042). Only 15% of all residents were able to identify 4 or more essential maneuvers. Higher level of training was associated with identifying the 2-person technique. In addition, residents who completed 1 month of pediatric or adult anesthesia were more likely to identify use of nasal airway, oral airway and 2-person technique, and to identify 4 or more maneuvers. CONCLUSIONS: Emergency medicine residents identified more steps to optimize difficult BMV, although most residents exhibited a poorly developed mental model for difficult BMV compared with the consistent mental model of airway experts. Future research should investigate strategies for improving residents' mental model of BMV and its impact on patient care.