A common language on CP has been developed for the European registers by the SCPE (Surveillance of Cerebral Palsy in Europe) working group and the common database allows prevalence analyses on a larger basis. CP prevalence increases with lower birthweight and higher immaturity. Increase of survival after preterm birth has first also increased CP rates. But already in the 80s this trend was reversed for LBW infants, and in the 90 s also for VLBW or very immature infants. The outcome with respect to CP in the group of extremely LBW or immature infants remains a matter of specific concern, as prevalence seems to be rather stable on a high level. CP is caused in more than 80% by brain lesions or maldevelopments which can be attributed to different timing periods of the developing brain. Extent and topography determine the clinical subtype of CP and are related also to the presence and severity of associated disabilities. CP, thus, offers a model to study plasticity of the developing brain. Reorganisation following unilateral lesions is mainly interhemispheric and homotopic. In the motor system, it involves the recruitment of ipsilateral tracts; functionality seems to be limited and decreases already towards the end of gestation. There is no clear evidence for substantial reorganisation in the sensory system. The best compensatory potential is described concerning language function following left hemispheric lesions. Language function reorganized to the right hemisphere eventually seems not to be impaired, this occurs, however, on the expense of primary right hemispheric functions.