MRI leukoaraiosis (LA) is less likely to interfere with simple compared to more complex working memory (WM) skills. We hypothesize that LA within the left hemisphere negatively impacts higher-level WM processes in dementia. Participants with dementia (n = 64; MMSE = 22.0 ± 3.4) performed a Backward Digit Task measuring simple storage/rehearsal (ANY-ORDER) and complex disengagement/temporal re-ordering (SERIAL-ORDER) recall. A visual rating scale categorized MRI-LA in five regions per hemisphere: frontal and parietal centrum semiovale, white matter around the frontal horns, body of the lateral ventricles and posterior horns. Amidst equivalent hemispheric LA scores [t(62) = -1.12, p > 0.05], correlations revealed an association between left-sided LA and SERIAL-ORDER recall (r = -0.31, p = 0.007) with LA around the posterior horn (ρ = -0.30, p = 0.008) and frontal centrum semiovale (ρ = -0.29, p = 0.01) showing the greatest association. Regression modeling confirmed the left posterior horn contribution to SERIAL-ORDER performance variance. Results suggest involvement of anterior (fronto-striatal) and more posterior (inferior parietal) white matter tracts in higher order WM deficits in dementia. © 2008 Elsevier Ltd.