Studies referring to changes in nutrient composition were carried out in a greenhouse in the years 2001-2002 during the growing of three cherry tomato cultivars (Lycopersicon esculentum var. cerasiforme Alef.): Conchita F1, Flavoriono F1 and Favorita F1. The plants were grown in coconut fibre slabs of 100x15x6 cm dimensions. The amount of a single nutrient dose depended on the developmental stage of the plant (from 60 to 180 cm-3 per plant) with about 15-20% overflow. During the growing, the chemical composition of nutrient solutions supplied to the plants and the drainage from the slabs were investigated. In the drainages, an increase of the concentration of Mn, Fe, Zn and P was observed. On the other hand, in the case of Cu and S-SO4, the results were not explicit. Because of high scale of sodium concentration, that element limited the amount of nutrient that could be applied in the recirculation system. High level of components in the drainage from the blocks indicated that in open systems during plant growing in that type of substrate it is advisable to apply 15-20% of nutrient overflow.