Cerebral palsy (CP) is a disorder with diverse causes that include early residual brain damage and non-progressive genetic disorders. Early treatment with multimodal, task-oriented rehabilitation has been shown to improve daily functioning and integration of affected children. However, early diagnosis is a prerequisite for early treatment. If, especially in preterm infants, the perinatal history was severe and brain damage was documented, early diagnosis of CP is straightforward. However, because more than 50% of CP patients had an unremarkable perinatal period after a full-term birth, valid risk predictors and clinical procedures for early diagnosis are needed in these cases. In addition to traditional testing for persistent primary neonatal reflexes and impaired muscle tone, a number of standardized tests have been developed that have high sensitivity and specificity for predicting impending CP and atypical development even in the first months of life. Neurodegenerative and metabolic disorders that progress slowly and have predominantly motor symptoms can mimic CP. Although rare, they should not be overlooked because of their importance in genetic counseling, treatment, and prognosis. The present chapter has been extensively revised with regard to early diagnosis, diagnostic workup, and differential diagnoses.