OBJECTIVE Takayasu's arteritis (TAK) is a chronic vasculitis, affecting predominantly the aorta and/or its major branches. The aim of this study was to compare the differences between childhood and adult onset TAK. METHODS We retrospectively evaluated 179 TAK patients followed between August 2005 and July 2019. Demographic characteristics, laboratory features, disease activity, echocardiographic data at diagnosis and treatment regimens in the disease course were compared between the paediatric and adult onset patients. RESULTS Twenty-five paediatric-onset (<18 years of age at diagnosis) and 154 adult-onset patients (≥18 years of age at diagnosis) were enrolled. The mean age at diagnosis for children and adults were 13.6±4 and 35.6±13, respectively. Paediatric onset TAK patients had more intense inflammation at the time of diagnosis reflected in their clinical findings. Acute phase reactants were high in all paediatric patients and significantly higher in patients with paediatric-onset TAK (p=0.006 and p=0.005, respectively). Abdominal predominant disease was more common in the paediatric group, in contrast, focal disease and aortic arch predominant disease were more common in the adult group. Ascending aortic dilatation, left ventricular hypertrophy and moderate-severe aortic insufficiency were more frequent in echocardiography findings of paediatric onset TAK patients. In comorbidities, hypertension was more common in paediatric TAK patients during follow-up, whereas cerebrovascular disease was more common in adult patients. CONCLUSIONS Our paediatric onset TAK patients presented with a more severe inflammation and more widespread vascular involvement. Multicentre studies from different geographic areas are needed to verify our observation and understand the underlying causes.