This dissertation consists of 11 chapters , subdivided into six chapters dealing with a paediatric and four chapters dealing with an adult population. This distinction between study populations is motivated by the fact that clinical symptomatology and semiology may differ in children and adults. Chapter I serves as an introductory overview on cerebellar anatomy, the traditional view on functions of the cerebellum, and the development of the concept "cerebellar neurocognition". Specifically, the role of the cerebellum in speech, language, and cognition will be discussed. Chapter II represents a literature review of the syndrome of cerebellar mutism and subsequent dysarthria, which is a well-known clinical entity that may occur in children who have undergone surgery for posterior fossa tumours. The aim of this chapter is to critically investigate the speech deficits reported in the literature in this specific patient population. In Chapter III, IV, and V the paediatric patients of the Erasmus MC/ Sophia's Children's Hospital (Rotterdam) and their speech and language disorders are described, subdivided into perceptual (Chapter III), acoustic analyses (Chapter IV), and language analyses (Chapter V). Chapter VI consists of a neurolinguistic, neuropsychological, and functional neuroimaging follow-up study of five paediatric patients recruited from the ZNA-AZ Middelheim Hospital (Antwerp). The diaschisis hypothesis as the pathophysological substrate for the occurrence of cognitive, linguistic, and behavioural disturbances was investigated with SPECT. In the subsequent chapters, language disorders in adults with focal cerebellar lesions are summarized, with first an overview of reported linguistic deficits in adults (Chapter VII). In Chapter VIII, the unique case study of a patient who presented with visual dyslexia and surface dysgraphia after a cerebellar infarction in the right superior cerebellar artery is described. In addition, a possible mechanism for this uncommon co-occurrence of reading and writing problems in a cerebellar patient is provided. In Chapter IX, two adult patients who developed apraxic agraphia after ischemic lesions in the cerebellum are reported. Vascular cases of apraxic agraphia were critically reviewed and the possible involvement of the cerebellum in the neural network of written language processing was explored. Finally, Chapter X represents the Dutch adaptation of the CAT. In order to test its clinical usefulness and to examine language disturbances in patients with cerebellar lesions, the CAT was administered in four cerebellar stroke patients with. In the final chapter of this dissertation (Chapter XI), the main findings are summarized, the primary implications of these research findings for formal speech and language therapy are outlined, and some future research prospects are presented.