Introduction. Electroconvulsive therapy (ECT) is the most effective treatment ill a variety of psychiatric syndromes (especially mood disorders). However one of its adverse effects is neurocognitive dysfunction. Declarative memory impairment after ECT is unquestionable and well investigated. There are only few ambiguous studies focused on nondeclarative and immediate memory changes during ECT. Method. A study of immediate (working) memory changes in depressed patients treated with ECT (n=10; bitemporal ECT 3 times a week) or imipramine or desipramine (150-250mg/day, n= 10) was conducted in patients who fulfilled DSM-IV criteria for major unipolar depression. Hamilton Depression Rating Scale (HDRS) and Beck's Depression Inventory (BDI) were used to assess the efficacy of antidepressant therapy. Cognitive functions were assessed with neuropsychological tests: Stroop A and B, TMT (Trial Making) A and B. The patients' status was evaluated 1 day before the treatment and 1 day, 2 weeks, 1 month and 6 months after the first ECT procedure. Results. 1 day after first ECT treatment, patient's working memory was slightly impaired, but this was not statistically significant. Both groups showed statistically significant improvement in working memory 1 month after start of treatment. However there were statistically significant differences between ECT and pharmacologically treated groups at the first month of therapy. Conclusion. ECT treatment only temporally affects working memory function. The improvement of function may be a result of clinical recovery from depressant symptomatology.