Cognitive disorders in the course of mental illnesses are one of the most important and most difficult therapeutic problems related to those illnesses and they regard attention, memory, learning and sensory modulation. The limited number of nicotinic receptors (subtypes alpha7 and alpha4beta2) seems to cause the incidence and exacerbation of cognitive deficits in such patients. In patients with schizophrenia, the impairment of cognitive processes is also a side-effect of neuroleptics. The characteristics and intensity of the negative effect of antipsychotics on cognitive functions depends on the pharmacological action of those drugs and on the effect on dopamine and serotoninergic receptors in particular. Cognitive function deficits observed in various mental illnesses can be modified with the use of nicotine. A cholinergic neurotransmission system is a common transmission system in the central nervous system. The effect of nicotine on other neurotransmission systems--the dopaminergic and glutaminergic systems--seems to be significant for their efficacious cognitive effects in combination with antipsychotic drugs. Nicotine may also alleviate symptoms of depression, as it amplifies serotoninergic and noradrenergic neuronal activity. When studies on treating cognitive disorders with nicotine are carried out, nicotine's interactions with other drugs used in therapy of those disorders must be taken into account as well as the effect of this substance on neurotransmission systems.