Increased life expectancy in patients with brain tumours has led to a greater risk of cognitive deficits, particularly during disease-free periods. Here, we review the empirical studies that have been done to treat or to prevent cognitive impairment in patients with brain tumours. Both pharmacological interventions and cognitive rehabilitation programmes have been used. Although both types of study have reported some successes, these are often difficult to interpret owing to limitations in the methods used. Most of the studies reviewed did not use a randomised group design to control for possible confounding factors such as placebo and practice effects. Investigations of newer, targeted therapies have reported delays in cognitive deterioration, but these need to be confirmed in future studies. Neuroprotection represents another potentially promising, novel approach to prevention of cognitive impairment in this vulnerable population of patients. Finally, we describe studies in patients with cancers outside the CNS, to highlight further possibilities for the prevention and treatment of cognitive deficits.