Objective: To evaluate the performance of a sample of postmenopausal women complaining of decline of prospective memory, undergoing therapy with concentrated extract of soy (CES) for six months, through specific neuropsychological assessment, developed for this purpose. Materials and Methods: A randomized and double-blind study was with 90 women, 12-month amenorrhea, 40 years to 65 years and body mass index (BMI) above 30 kg/m 2 , whose complaints were reduction of cognitive efficiency. The participants were randomly divided into two treatment groups: Group I-received one capsule of 150 mg extract of soy, with 60 mg isoflavones orally/day; Group II-received one capsule placebo, for six months. All participants underwent a detailed interview, the MMSE, depression scale, and as they were being included in the study, self-perception scales and neuropsychological tests before and after six months of treatment. For analysis purposes, we applied the ANOVA and t-student tests. Results: Our results suggest a possible positive effect regarding the improvement in verbal fluency and executive function tasks of planning and mental flexibility, in women undergoing therapy with concentrated extract of soy in postmenopause. There was no correlation between prospective memory and cognitive performance, and there were only intensity scores of the depressive symptoms. Conclusion: Isoflavones act favorably on the cognitive function, amongst all functions, only on verbal memory and executive function tasks of planning and mental flexibility. The others showed no signs of improvement. We concluded that concentrated extract acts only on some cognitive functions.