Background: Sedation of critically - ill children in Paediatrics Intensive Care Units (PICU) is an essential component of patient care. The Bispectral Index (BIS) is a non-invasive electroencephalographic technique that measures continuously the hypnotic effects of various sedative agents. Objective: Evaluate Bispectral Index technology on ventilated patients in PICU and determine the degree of correlation with COMFORT Scale. Method: Prospective - blinded - observational study, where sedate children were evaluated in their sedation level by using BIS monitor and COMFORT Scale. BIS values were categorized in very deep (< 40), deep (41-60), moderate (61-80) and light (> 80) levels of sedation. Results: 9 patients were enrolled in the study, obtaining 180 valid-paired observations of BIS values and COMFORT Scale scores. The median COMFORT Scale and BIS values were 17 (range 11-29) and 48 (range 18-90), respectively. The correlation coefficient between BIS and COMFORT Scale in the individual measurements was good (R = 0.74). When BIS measurements were categorized in light, moderate, deep and very deep sedation levels, the BIS and COMFORT Scale measurements were highly correlated (R = 0.92). 72% of BIS observations were above adequate sedation levels. Conclusions: There is a good correlation between BIS and COMFORT Scale. BIS may be a useful tool in sedation assessment on ventilated paediatric patients, identifying excessive sedation in PICU