The aim of this study was to assess the effect of donepezil on cognitive functions in patients with Alzheimer’s disease (AD) previously treated with rivastigmine. Thirty-one AD patients, 11 males and 20 females, aged 56-86 (mean 71 years), with duration of illness 2-4 (mean 3 years) and duration of rivastigmine treatment 3-12 (mean 8 months) participated in the study. Compared with the results obtained before donepezil administration, a significant improvement in Mini Mental State Examination score (after 3 and 6 months), Alzheimer Disease Assessment Scale (ADAS-cog) and Trail making Test (TMT) A after 3,6 and 12 months of treatment was found. No improvement was observed on TMT B, measuring the efficiency of visuo-spatial working memory and in both parts of Stroop test, measuring the efficiency of verbal working memory. The results obtained suggest a positive effect of donepezil on global cognitive functioning in patients with AD previously treated with rivastigmine who had insufficient improvement or did not tolerate the drug. Donepezil may also slow down the progression of deterioration of cognitive functions connected with frontal lobe activity in AD patients.