Differences in brain structures involved in gait control between normal and pathological aging are still matter of debate. This study aims to compare the regional and global brain volume patterns associated with gait performances assessed with Timed Up and Go test (TUG) between cognitively healthy individuals (CHI) and patients with mild cognitive impairment (MCI). Material and methods A total of 171 (80 CHI, 25 with amnestic MCI [a-MCI] and 66 with non-amnestic MCI [na-MCI]) participants (70.2±4.0years; 37% female) consecutively realized (rTUG) and imagined (iTUG) the TUG. rTUG measures the time needed to rise from a chair, walk 3m, turn around and return to a seated position and iTUG represents the validated imagined version of the TUG. Global and regional brain volumes were quantified from three-dimensional T1-weighted MRI using a semi-automated software. Results Linear regression models show that increased rTUG (i.e. worse performance) was associated with lower total white matter, total gray matter, left and right hippocampal volume in patients with na-MCI (P\textless0.045), and with lower right hippocampal volume in CHI (P=0.013). Increased iTUG was associated with lower gray matter and left premotor cortex volumes in patients with na-MCI (P\textless0.05). Conclusions The findings showed different patterns of brain volume reduction associated with increased rTUG and iTUG between CHI and MCI patients, except for the right hippocampal volume which was smaller in both groups.