Background/Aim: Anti-cancer therapies may deteriorate cognitive functioning, affective functioning and psychological well-being. Materials and Methods: In this prospective longitudinal pilot study, premenopausal and postmenopausal patients received adjuvant endocrine therapy (ET) (tamoxifen with or without LHRH analog or aromatase inhibitor) or were observed only (control group). At baseline testing and 6, 12 and 24 months thereafter, cognitive, depression and anxiety tests and quality of life (QOL) measurements were performed. Results: Overall, 46 cases were evaluated. None of the studied cognitive parameters differed between the subgroups or changed by time. No differences were found regarding anxiety, depression or QOL measures either. Baseline cognitive test and QOL results were in association with later anxiety and depression. Conclusion: No cognitive impairment was found during the two years of ET. Baseline cognitive scores and QOL dimensions proved good predictors of later anxiety and depression.