Cerebral venous thrombosis may be well tolerated or lead to a brain lesion; availability of collateral venous pathways may explain the great variability of the lesions. This collateral circulation involves mainly medullary and cortical veins. These are difficult to assess neuroradiologically, particularly if thrombosed. Cerebral venous thrombosis is diagnosed usually based on thrombosis of dural sinuses and of the deep venous system. We tried to correlate the site and extent of dural sinus thrombosis with the location and the size of brain lesions in 26 consecutive patients with cerebral venous thrombosis, to investigate whether a simple causal relationship exists. No significant correlation between the extent and site of thrombosis in dural sinuses and the extent and location of brain lesions was found. In some cases a clear relationship between thrombosis of cortical and medullary veins and the lesions was evident. These data suggest that sinus thrombosis alone may be well tolerated in many cases, while involvement of cortical and medullary veins leads to a worse clinical situation.