Effect of ovarian steroids on serotonin neurotransmission suggests that the modulating effect of polymorphisms of the serotonin transporter gene on brain activity in women may change with age related changes in hormonal status. Objective of the study was to identify relationships between 5-HTTLPR polymorphism of the serotonin transporter gene and characteristics of baseline EEG in healthy young women (19-35 years, N = 85) and in women in post menopause (55-80 years, N = 44). It was shown that in S'/S'(SA/SA, SA/LG) and L'/L' (LA/LA) genotypes carriers' women of the older age group had lower delta, alpha 2 and alpha 3 band power than the young. In older women genetic differences in the power of these rhythms were due to lower values in carriers of S'/S' and L'/L' compared with S'/L' genotype. S'/L' genotype was characterized by higher beta 1 rhythm power in elderly compared with young women. These results demonstrate the difference in the neurophysiological mechanisms of age-related changes in brain activity which are associated with the polymorphism of 5-HTTLPR.