There are several subtypes of degenerative dementia which result from different pathogenic protein aggregations. The accurate diagnosis and differential diagnosis of dementia subtypes are critical important for it relates to the disease treatment and prognosis. Neuropathological finding is the gold standard for diagnosis of degenerative dementia. However, it is infeasible to apply this study in the clinical practice. Recently advanced molecular imaging provided complementary information to help clinician in diagnosis of dementia. From anatomical study, using structural imaging tool such as computerized tomography (CT) or magnetic resonance imaging (MRI) could provide a different atrophic pattern for dementia classification. Typical Alzheimer’s disease dementia (AD) showed a predominant atrophy in the hippocampus. The behavioral variant of fronto-temporal dementia (bv-FTD) and primary progressive aphasia (PPA) showed orbitofrontal and left perisylvian atrophy pattern respectively. Fronto-parietal atrophy could be found in cortico-basal syndrome. Molecular imaging using different ligends could help clinician to early detect the minimal changes even the structural atrophy become apparent. The most common molecular brain image used in dementia study is the fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET), which assess the resting state cerebral metabolism. Its decrease uptake in temporo-parietal region is a neuronal injury biomarker for diagnosis of AD. In dementia with lewy body (DLB), both the cingulate island sign (CIS) and decreased uptake in occipital region are typical presentation. Finally, various new PET tracers had been developed to explore the different pathological biomarker in neurodegenerative disease such as amyloid marker (e.g Pittsburgh compound-B (PiB), florbetapir(AV-45) and florbetaben), tau marker (e.g FDDNP, THK523, THK5105 and THK5117) and monoamine marker (AV-133). These agents, combine with high resolution anatomical image could improve our knowledge related to the pathophysiological process of the different degenerative dementia.