Abstract BACKGROUND Children with a supratentorial midline Low Grade Glioma (LGG) may be at risk for impaired bone health due to hypothalamic-pituitary dysfunction, obesity, exposure to multiple treatment modalities, and/or decreased mobility. The presence of impaired bone health and/or its severity in this population has been understudied. We aimed to identify the prevalence and risk factors for bone problems in children with supratentorial midline LGG. METHODS A retrospective study was performed in children with supratentorial midline (suprasellar or thalamic) LGG between 1-1-2003 and 1-1-2022, visiting the Princess Máxima Center for Pediatric Oncology. Impaired bone health was defined as presence of vertebral fractures or collapse, any fractures not related to (the intensity of) trauma, treatment with bisphosphonates, and/or very low bone mineral density (BMD). RESULTS In total, 161 children were included, with a median age at tumor diagnosis of 4.7 years (range 0.1 – 17.9) and a median follow-up of 6.1 years (range 0.1 – 19.9). ‘Any’ bone problem occurred in 22.4% (36/161) and nontraumatic fractures in 3.7%. Impaired visual capacity was associated with bone problems in multivariate analysis (OR 3.56 95% CI 1.30 – 9.76, p = 0.014). CONCLUSIONS In this retrospective evaluation, bone problems and decreased BMD were prevalent in 36.1% of children with supratentorial midline LGG. Risk to develop bone problems appears to be multifactorial, but visual capacity seems highly relevant. Surveillance of bone health must be an aspect for awareness in the care and follow-up of children with a supratentorial midline LGG.