Docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid, has significant healthbenefits. Previous studies reported decreased levels of DHA and DHA-containing phosphatidylcholines inthe brain of animals suffering from Alzheimer's disease, the most common type of dementia; furthermore,DHA supplementation has been found to improve brain DHA levels and memory efficiency in dementia. Oilextracted from the seeds of Plukenetia volubilis (green nut oil; GNO) is also expected to have DHA like effectsas it contains approximately 50% α-linolenic acid, a precursor of DHA. Despite this, changes in the spatialdistribution of DHA in the brain of animals with dementia following GNO or DHA supplementation remainunexplored. In this study, desorption electrospray ionization imaging mass spectrometry (DESI-IMS) wasapplied to observe the effects of GNO or DHA supplementation upon the distribution of DHA in the brain ofmale senescence-accelerated mouse-prone 8 (SAMP8) mice, a mouse model of dementia. DESI-IMS revealedthat brain DHA distribution increased 1.85-fold and 3.67-fold in GNO-fed and DHA-fed SAMP8 mice,respectively, compared to corn oil-fed SAMP8 mice. Memory efficiency in SAMP8 mice was also improvedby GNO or DHA supplementation. In summary, this study suggests the possibility of GNO or DHAsupplementation for the prevention of dementia.