We describe the cognitive profile in a complete national cohort of children with cerebral palsy (CP). One hundred and twenty-seven Icelandic children (67 females, 60 males) with CP, born between 1985 and 2000 and assessed between the ages of 4 and 6 years 6 months (mean age 5y 5mo, SD 6mo), were included in the study. IQ was measured using the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) and developmental quotient (DQ) was obtained using various developmental scales. Physiological classification of CP in the children was: spasticity, n=104 (82%); dyskinesia, n=14 (11%); ataxia, n=six (4.7%), and unclassified CP, n=3 (2.3%). Spastic diplegia was the most prevalent subtype (35%) followed by hemiplegia and quadriplegia. Forty-five per cent of the group were at Level I of the Gross Motor Function Classification System, 32% were at Levels II and III, and 23% were at Levels IV and V. Sixty per cent of the children had an IQ or DQ greater than 70. Median scores on the WPPSI were Full-scale IQ 84, Verbal IQ (VIQ) 92, and Performance IQ (PIQ) 77. Children with spastic diplegia and quadriplegia had a significantly lower PIQ than VIQ. Of the children who failed to complete the WPPSI, 20% had DQ greater than 85. Thus, cognitive skills can be masked by limitations of movement and motor control in children with CP.