This chapter focuses on the group differences between disorders and highlights the role of structural and functional imaging in non-Alzheimer dementias. Modern imaging techniques have allowed for structural and functional analysis of patients with frontotemporal dementia-behavioral variant (bv-FTD). In searching for an imaging biomarker for FTD or frontotemporal lobar degeneration (FTLD), functional brain imaging studies, including both single-photon emission computed tomography (SPECT) and positron emission tomography (PET), represented a significant step forward in the clinical diagnosis of bv-FTD. FDG-PET studies in semantic dementia (SD) patients have shown dysfunction in the bilateral temporal regions and medial orbitofrontal regions. Volumetric magnetic resonance imaging (MRI) studies in individual patients with progressive non-fluent aphasia (PNFA) have shown minimal atrophy, left perisylvian atrophy, or left-hemispheric atrophy. The first antemortem diagnostic tests for Creutzfeldt-Jakob disease (CJD) came from cerebrospinal fluid analysis and elecroencephalography (EEG).