This chapter provides a comprehensive overview of hemiplegic forms of cerebral palsy (CP), focusing on their etiopathogenetic, clinical, and functional classifications. Hemiplegia, defined as a central unilateral, mostly spastic motor impairment, is the most common CP form in term-born infants and the second most frequent in preterm infants. Four main clinical forms are identified—early malformative, prenatal, connatal, and acquired—based on lesion type and timing. Advances in neuroimaging, particularly magnetic resonance imaging (MRI), have significantly enhanced understanding of lesion patterns and brain reorganization processes. These reorganization mechanisms, either ipsilesional or contralesional, vary depending on lesion timing and extent, with ipsilesional patterns generally leading to better functional outcomes. The chapter discusses sensorimotor system reorganization, highlighting the critical role of early motor activity and somatosensory integrity in shaping corticospinal projections. It also reviews a wide range of standardized assessment tools for upper limb function, framed within the International Model for Classification of Functioning, Disability and Health (ICF) model (body functions, activities, and participation). A clinical five-pattern classification of hand manipulation in children with spastic hemiplegia is proposed and validated, showing strong reliability and correlation with existing clinical scales. This classification supports individualized assessment and intervention planning, helping clinicians better characterize hand function and guide rehabilitation in children with unilateral CP.