Brain volume is commonly found in dementia both Alzheimer’s dementia (AD) and non-Alzheimer’s dementia (NAD). Clinical decision-making could be supported by identifying differences in brain parameters. This study investigates brain volume differences among individuals with normal cognition (NC), AD, and NAD using structural magnetic resonance imaging (MRI) and automated analysis with FreeSurfer. The aim is to identify brain parameters to differentiate between each group. A total of 76 participants were categorized into NC, AD, and NAD groups, and their brain scans were processed to obtain absolute brain volume and brain volume normalized by intracranial volume (ICV). The left amygdala/ICV ratio demonstrated excellent performance in discriminate between AD and NC, with a cutpoint of ≤ 0.100466706 providing 100 % sensitivity, 83.30% specificity, and 0.968 of area under the curve (AUC). For NAD vs. NC, a cutpoint of ≤ 0.098023101 provides 100% sensitivity, 85.40% specificity, and 0.947 of AUC. However, there is no brain parameter achieve AUC over 0.8 for classification between AD and NAD. These findings suggest that reductions in brain volume correlate with cognitive decline. Utilizing FreeSurfer and MRI data, particularly the left amygdala/ICV, can aid in distinguishing normal cognition from both AD and NAD.