In Croatia, the main substrate in hydroponic tomato production is rockwool. It is quite a popular choice among producers, because of its good properties and uniform results. Due to the increase in the area under hydroponic cultivation, used rockwool is an environmental problem because of its inorganic origin, therefore, it slowly decomposes. The way that this problem can be reduced is to use organic substrates available on the local market. The aim of this research was to investigate the influence of local organic and mixed substrates on the yield components of tomatoes and to compare it with the results obtained on rockwool. The study was carried out in heated greenhouse at the Department of Vegetable Crops, Faculty of Agriculture in Zagreb. Two cluster cultivars were used, Amaneta and Fabiola, and cherry cultivars Sakura and Tropical. Transplants of four cultivars, grown in rockwool cubes, were planted on the rockwool slabs and bags of organic and mixed substrates in the first decade of May. For each plant was determined the number of fruits, the weight of marketable fruits, yield and share of non-marketable fruits. It was determined that different substrates didn't affect the weight of marketable fruits, yield and share of non-marketable fruits, but there was a significantly higher number of fruits on tomato plants that were grown on rockwool. The average number of fruits was 217 per plant. There was a significant interaction between tomato cultivars and substrates. The largest fruits were harvested from the cultivar Amaneta on a mixed substrate (160 g), and on the same substrate, Amaneta had the largest share of non-marketable fruits (33.7%). Fabiola had the highest yield on the mixed substrate, 4600 g per plant, while the lowest yield was achieved by "cherry" cultivar Tropical on the organic substrate, 1917 g per plant.