In the years 2004-2005, studies of the influence of substrate and cultivar on greenhouse tomato yield were conducted. In the two-factorial experiment established in randomized complete block design the following factors were studied: substrate – rockwool, wood fibre and highmoor peat, as well as cultivars – Emotion F1 and Grace F1. High suitability of these substrates for greenhouse tomato growing was shown. Total yield obtained from cultivation on wood fibre amounted to 18.86 kg m-2, on highmoor peat – to 18.70 kg m-2, and on rockwool – 19.44 kg m-2. The marketable yield showed considerable differenced between cultivars and years of cultivation. Emotion F1 proved to be a better cultivar and its marketable yield amounted to 18.77 kg.m-2, while for Grace F1 it was 16.04 kg m-2. The percentage of marketable yield in total yield, depending on the substrate used, ranged from 84.8 do 87.8%. Yield structure for individual fruit selections obtained for plants grown on rockwool amounted to 76.6% for selection IA, 9.9% for IB, and 1.5% for II. Emotion F1 cultivar was characterized by higher percentage of IA (76.2), IB (11,8%) and II (1,5%) than Grace F1 cultivar (74.7, 7.8 and 0.8%, respectively).