Clinical validation of blood pressure oscillometric devices are almost exclusively conducted in adults. Because oscillometric devices are used in children, it is critical to assess their accuracy also in this population. We compared blood pressure readings using an oscillometric automated device (Dinamap XL, model CR9340) with readings obtained with the mercury auscultatory method in children and adults. Blood pressure was measured in 30 children (15 boys and 15 girls; 9.5+/-1.0 years old) and their parents (25 mothers and 15 fathers; 41.0+/-5.0 years old). In children, mean difference (+/-SD) in systolic blood pressure (DeltaBP) readings (oscillometric-auscultatory) was +0.6+/-4.7 mmHg (range: -10 to +11); mean diastolic DeltaBP was 21.3+/-7.5 mmHg (range: -18 to +19) and decreased with increasing diastolic BP. In adults, mean systolic DeltaBP was +0.4+/-5.2 mmHg (range: -12 to +15) and mean diastolic DeltaBP was -5.2+/-6.0 mmHg (range: -25 to +8) (p<0.001). While the device was not accurate enough to be recommended, our study also shows that the accuracy of blood pressure oscillometric devices can differ between children and adults. Clinical accuracy of oscillometric devices should be tested in the specific populations in whom blood pressure is measured.