Kneeblocks are used to create a symmetric sitting position for individuals with different physical disabilities. The aim of this paper was to examine the impact of kneeblocks in children with cerebral palsy. Six children aged 4-13 years (mean 9 years) participated in the study. Pressure applied to the children's legs was measured with a computer aided system with waterfilled plastic bags and a pressure transducer with 2 Hz registration continuously during 3 minutes. The registrations were made in four difference sitting positions - horizontal sea and 5 degrees forward inclined, seat with and without a hipbelt, while the children performed different standardised tasks at a table. This was documented by videofile and photographs. The results were presented for the different sitting positions and tasks. The means pressure varied from 0.5 kPa in the sitting position with horizontal seat with a hipbelt to 5.2kPa in the position with 5 degrees forward inclined without a hipbelt. Occasionally pressure up to 24.5 kPa was measured. The kneeblocks did constantly exert pressure on the children's legs, but the pressure varied. If kneeblocks are used it should be in combination with a hipbelt, to minmise the pressure applied to the children's legs.