Unanticipated difficult airway comprises of unexpected difficult bag mask ventilation or unforeseen difficult laryngoscopy. The incidence of difficult laryngoscopy or unanticipated difficult intubation in children was varied from 1.2 %to 4.77% depending on general or specific population and type of surgery. The known risk factors of difficult intubation in children were young age, associated syndrome or congenital abnormality and obstructive sleep apnea. Moreover, the predictors of difficult laryngoscopy by physical examination were associated with short interincisors distance, high frontal plane to chin distance, short thyromental distance and Cormack & Lehane classification 3 or 4. However, little knowledge is known regarding difficult bag mask ventilation in children. The incidence of difficult bag mask ventilation was 6.6% according to the single study. A few study reported the independent risk factor of difficult bag mask ventilation in children which were young age, obesity, use of neuromuscular blocking agent and airway surgery. In addition, the association between difficult bag mask ventilation and difficult intubation are still unknown. To understand more of difficult bag mask ventilation in children and factor-association may reduce incidence of morbidity and mortality by identifying difficult airway, preparing personnel and equipment tool in order to improve clinical outcome in pediatric anesthesia. The objectives of the study were to determine the predictors of difficult bag mask ventilation and the association with unexpected difficult intubation in children who came for elective surgery in tertiary care hospital of southern Thailand.