Aiming the investigation of potential differences in accuracy of the algorithms of pediatric anesthesia in everyday practice, 338 children where studied, from newborns to 14 years old, who underwent scheduled or emergency operations in a 3 months period,. They were divided according to their age into 4 groups (38 newborns and infants, 43 children from 1 to 3 years old, 90 children from 3 to 6 years old, 167 children >6 years old). Someone of the authors was recording the demographic data (gender, age, weight, height) and other parameters before anesthesia (SAP, HR, Haematocrit, fasting period) and was estimated the proposed ETT size with Δ1=(age/4)+4 and Δ2=(18+age)/4 algorithms and the ETT insertion length (from the barrier of the teeth) with M1=(age/2)+12 and M2=(internal diameter ETT)*3 algorithms. In the grand total of children significant differences were found between the predicted and the measured values of weight (p<0,001), SAP and HR (p<0,001), preoperative fasting period (p<0,001), internal diameter of the ETT with Δ1 (p<0,001) and Δ2 (p<0,001) and the ETT insertion length with M2 (p<0,001). Conclusively the children in the present study were found overweighted, with highest than the predicted SAP and HR. The preoperative fasting period was longer than the recommended. The Δ1 algorithm underestimates the internal diameter of the ETT really needed, while the Δ2 overestimates it. The ETT insertion length is estimated accurately by the M1, while it is overestimated with the M2.