Background Endotracheal suctioning is a significant aspect of the care of intubated child, however this procedure are associated with many risks. Aim: to evaluate the effect of closed versus open suction on cardiorespiratory parameters in mechanically ventilated children. Design: A quasi-experimental research design was used. Sample: Apurposive sample of 60 children aged (2 to 7years' old) who met the inclusion criteria at PICU of Assiut University Children Hospital. They were selected randomly and divided into two groups: Group I: Included 30 children for whom open suction method was used. Group II: Included 30 children for whom closed suction method was used. Tools: One structured toolwas utilized tocollect the relevant data which include: Structure questionnaire sheet which divided into three parts, Personal characteristics, Medical data, and cardiorespiratory parameters of children record. Results: Highly statistical significance difference between open and closed suction method regarding cardiorespiratory parameters during and immediately after suction (P. <0.001**).However, there were no statistically significant differences in ABG parameters before and after suction in both open and closed suction groups. (P. 0.33, 0.29, 0.688) Conclusion: Closed suction method is more effective than open suction method in daily practice. So, theresearcher Recommendation: Closed suction method should be incorporated as one of the best method of suction on reducing hemodynamic instability in daily practice.