The prevalence of bipolar disorders is about 4% of the population. Among the patients the emergence of cognitive disorders has been identified. These disorders can sometimes result in authentic dementia-like syndromes. The neuropsychological characteristics of the cognitive impairment include disorders of the steady attention, executive functions, memory and language. This group of cognitive disorders leads to a subcorticofrontal syndrome. Different neuroanatomical bases have been suggested. The most common etiopathogenic hypothesis retains a cumulative neurological toxicity of the thymic episodes (depression or mania). The role of psychoactive treatments must be taken into account. The secondary cognitive effects of psychoactive drugs usually used in bipolar disorder (lithium, antiepileptics, antidepressants, antipsychotics or tranquillizers) are similar to the cognitive impairment associated with the disease. Differentiation between cognitive disorders related to the pathology and those related to its treatment is difficult. The optimal use of the therapeutic drug classes, preferring antipsychotics of second generation and avoiding products with anticholinergic effect, is essential. There is no specific pharmacological treatment for this dementia syndrome. Psychological approaches offer an alternative way of care, which remains to be investigated and validated. Prevention of iatrogenic effects of drugs constitutes, presently, the main therapeutic intervention.