This thesis investigates the role of volumetric MRI in the diagnosis and measurement of progression in patients with frontotemporal lobar degeneration (FTLD). Patterns of regional atrophy were assessed cross-sectionally using both visual ratings and the automated unbiased technique of voxel-based morphometry (VBM). Both techniques identified characteristic patterns of atrophy in FTLD, and its syndromic variants. In addition, a network of structures was identified that may contribute to the behavioural abnormalities observed in FTLD patients. Detailed regional volumetric measurements of temporal lobe structures were performed in both clinically and pathologically diagnosed patients with FTLD and Alzheimer's disease (AD). Characteristic patterns of atrophy were identified in both groups that may be useful in the differential diagnosis of FTLD and AD. Patterns of atrophy in the different pathological subtypes of FTLD were also assessed using VBM. Significant differences were observed between groups suggesting that imaging may also be useful in predicting the underlying pathological substrate of FTLD.