Background: Cerebellar atrophy is a neuroradiol. definition that categorizes conditions heterogeneous for clin. findings, disease course, and genetic defect. Most of the papers proposing a diagnostic workup for pediatric ataxias are based on neuroradiol. or on the literature and exptl. knowledge, with a poor participation of clinics in the process of disease definition. Our study aims to offer a different perspective on the way we approach cerebellar atrophy in developmental age, building a clin.-based diagnostic workup to guide mol. diagnosis. Methods: we recruited 52 patients with pediatric-onset cerebellar atrophy and definite disease categorization. Children underwent brain MRI, neurophysiol. exams, metabolic investigations, and muscle biopsy with respiratory chain complex study. Single-gene sequencing, next-generation sequencing NGS panels, whole-exome sequencing (WES), and disease-specific techniques have been used to reach genetic confirmation. Results: Brain MRI is the main method of diagnosis, followed by tests on muscle biopsy and peripheral nervous system study. Other exams (e.g., metabolic investigations or evoked potentials) may be useful to narrow the list of diagnostic possibilities. Conclusions: We propose a diagnostic approach to cerebellar atrophy in children based on clin. findings, and support the evidence that a precise phenotypic definition may lead to the formulation of a definite diagnosis or otherwise guide the back phenotyping process derived from large mol. data.