On ten certified organic farms in Kurpie, Podlasie and Brodnickie Lake regions the experiments were carried out to compare the field performance and yielding potential of 35 currently cultivated and old cultivars or populations: 11 bread wheat (Triticum aestivum L.), 4 spelt wheat (Triticum spelta L.), 7 emmer wheat (T. dicoccon Schrank), 1 einkorn wheat (T. monococcum L.), 5 barley and 7 oats. Seeds were sown on plots of 1 m². Plants were surveyed with respect to phases of growth, disease resistance, lodging resistance and yielding parameters. Two-year results showed that mean level of yielding under organic farming obtained by old, husky wheat cultivars spelt and emmer, was similar to that of the average modern bread wheat cultivars. It was twice higher than the yield given by einkorn. The best yielding potential under organic farming conditions showed modern bread wheat cultivars - Eta and Hera, T. spelta var. album of spelt wheat and old cultivar Bazylei of emmer wheat. Only modern cultivars of barley were characterized by high yielding potential and disease resistance,while in the oats of both, modern and old cultivars, showed highest yielding and disease resistance. Out of all surveyed cereal species the oats tend to be best adapted to organic farming conditions, especially at poor soil conditions.