The main objetive was to compare 30:2 and 15:2 compression-to-ventilation ratio in two simulated pediatric cardiopulmonary resuscitation (cpR) models with single rescuer. the secondary aim was to analyze the errors or omissions made during resuscitation. A prospective randomized parallel controlled study comparing 15:2 and 30:2 ratio in two manikins (child and infant) was developed. The CPR was performed by volunteers who completed an basic CPR course. Each subject did 4 CPR sessions of 3 minutes each one. Depth and rate of chest compressions (CC) during resuscitation were measured using a Zoll Z series defibrillator. Visual assessment of resuscitation was performed by an external researcher. A total of 26 volunteers performed 104 CPR sessions. Between 54-62% and 44-53% of CC were performed with an optimal rate and depth, respectively, with no significant differences. No differences were found in depth or rate of CC between 15:2 and 30:2 compression-to-ventilation ratio with both manikins. In the assessment of compliance with the ERC CPR algorithm, 69.2-80.8% of the subjects made some errors or omissions during resuscitation, the most frequent was not asking for help and not giving rescue breaths. the conclusions were that a high percentage of cc were not performed with optimal depth and rate. errors or omissions were frequently made by rescuers during resuscitation.Pediatric cardiac arrest (CA) is an important health problem since it has high mortality (52-80%) and a large proportion of survivors suffer from permanent and severe neurologic disability (poor outcome in 20-50%) 1-4 . Previous studies have shown that optimizing maneuvers of cardiopulmonary resuscitation (CPR) in children could improve survival and prognosis 4,5 . Nevertheless, many studies documented that CPR is often not optimally performed 6,7 .The 2015 European Resuscitation Council (ERC) guidelines recommend a synchronized 15:2 compression-to-ventilation ratio during basic pediatric CPR 1,8,9 . However, there is not a strong evidence to indicate the best compression-to-ventilation ratio in pediatric CPR 10,11 . Firstly, maintaining an adequate ventilation is crucial during CPR in children because pediatric CA is primarily caused by respiratory failure 2 . The 15:2 ratio delivers more ventilations whereas the 30:2 ratio delivers more chest compressions (CC). In the other hand, different recommendations for the compression-to-ventilation ratio between children (15:2 ratio) and adults (30:2 ratio) could increase the errors or omissions and impair learning. In adult simulation models 12-14 , there are different studies that compare the quality of CC in both compression-to-ventilation ratio. However, only one study conducted in pediatric models, but it was developed by volunteers with pediatric advanced life support (PALS) accreditation 15 . In our knowledge, there are no previous studies comparing the quality of CC between 15:2 and 30:2 compression-to-ventilation ratio during pediatric CPR conducted by volunteers training in basic life support.with ...