OBJECTIVE:: We sought to assess whether magnetic resonance imaging (MRI) at 3.0 T detects more brain lesions in acute optic neuritis (ON) than MRI at 1.5 T. MATERIALS AND METHODS:: Twenty-eight patients with acute ON were scanned at both field-strengths using fast-fluid-attenuated inversion recovery (FLAIR), proton density and T2-weighted turbo spin echo, and T1-weighted spin echo after contrast. In addition, magnetization-prepared rapid acquisition gradient echo (MPRAGE) was obtained after contrast at 3.0 T. Lesion number and volumes were assessed by an observer blind to patient identity and field strength. RESULTS:: Scans at 3.0 T showed a significantly increase in number of lesions detected on FLAIR images (P = 0.002) relative to scanning at 1.5 T. MPRAGE proved to be suitable for detecting enhancing lesions in ON. CONCLUSION:: The MRI protocol at 3.0 T was more sensitive to hyperintense brain lesions in ON than the standard MRI protocol at 1.5 T