The aims of this retrospective and population-based study were to describe the frequency and characteristics of epilepsy in 146 children (82 males and 64 females) with cerebral palsy (CP) born from 1987 to 1994 in the Göteborg area of Sweden. The frequency of epilepsy was found to be 38% (55 children). All children with tetraplegic CP and about one-third of the children with other CP types developed epilepsy. Age at onset of epilepsy varied with type of CP: children with tetraplegic CP tended to have an earlier onset of epilepsy than children with other CP types. Partial seizures were the most common seizure type; all children with hemiplegic CP had partial seizures. Children with cognitive impairment had a higher frequency of epilepsy than those without cognitive impairment. CP aetiology may predict the development and outcome of epilepsy, as children with CP caused by CNS malformation, CNS infection, and grey matter damage all showed a higher frequency of epilepsy than children with CP of other aetiology, and also had less chance of becoming seizure-free.