Strategic infarcts or focal hemorrhages involving the paramedian nuclei of the thalamus may alter consciousness and produce complex neuropsychological symptoms such as impairment of memory, attention and motivation. Lesions disrupting the thalamo-prefrontal circuits lead to severe subcortical dementia. We analysed here the clinical, neuropsychological and neuroimaging data of 19 patients with cerebrovascular lesions in the thalamus. In six patients with bilateral paramedian infarcts, and in two with anterior thalamic infarcts, vascular dementia and severe personality changes developed. SPECT findings did not correlate with the neuropsychological symptoms. Transcortical sensory and motor aphasia was observed in four patients with thalamic hemorrhages and infarcts. In these patients SPECT detected hypoperfusion in adjacent cortical areas. Clinical symptoms and outcome of four patients are reported in detail. The clinico-morphological correlations of the thalamo-cortical circuits are reviewed and the possible causes of multiple cognitive and behavioural consequences of vascular thalamic lesions are discussed.