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Leber Hereditary Optic Neuropathy (LHON) is a mitochondrial genetic condition that results in painless, often sequential, severe visual loss. In children it can present insidiously and is frequently challenging to diagnose. There are limited reports of MRI findings in acute LHON, especially in children. We present two such paediatric patients. Case 1: A 7-year-old boy with bilateral dense vision loss was diagnosed with LHON and found to be homoplasmic for m.14484T>C mitochondrial DNA mutation. MRI of the brain and orbits showed a swollen optic chiasm with central T2 hyperintensity and contiguous signal abnormalities in both optic nerves, with faint enhancement following contrast. He was treated with idebenone and central visual acuity improved in both eyes to 0.0 logMAR. Case 2: A 15 year-old boy presented with left painless dense visual loss. His older brother was known to be homoplasmic for m.11778A>G. A MRI brain was undertaken in the acute phase and showed T2 hyperintensity, swelling and faint enhancement affecting the left optic nerve, left chiasm and left optic tract. The right eye has become affected six months later, despite taking idebenone. Case reports/series of MRI findings in acute LHON are mostly in adults but also report T2 hyperintensity of the optic nerves, as well as chiasmal swelling, but without enhancement. There is little evidence in the literature for MRI findings in acute LHON in children. It is important to highlight acute MRI changes in children with LHON as these can resemble inflammatory optic neuropathy and result in misdiagnosis.