This research was carried out in an unheated PE tunnel during autumn and spring seasons of 2006 and 2007 to determine the response of tomato to different EC levels of nutrient solution in closed system. Tomato (cv. Durinta) plants were grown in cocopeat with a plant density of 3.5 plants m-2. Plant root volume was 6 liters per plant. Plants were fed with a complete nutrient solution at the electrical conductivity levels of (1) 2.0 (control), (2) 4.0 and (3) 6.0 dS m-1. Salinity level of the nutrient solution was increased three weeks after planting by NaCl. Irrigation was based on indoor solar radiation level of 2 MJ m-2. Irrigation water volume was determined by leaching ratio which was kept around 25% in control treatment (LF1) and the same amount of solution was applied to the other treatments. In LF2 treatments nutrient solution was increased by 30% of LF1. Recirculating solution was replaced if the EC level was found to exceed the initially set level by two units for each treatment. Total yield, harvested fruit number, average fruit weight, fruit size and water consumption were determined. Additionally, crop coefficients were developed on a daily basis for growing season. The results showed that fruit yield and water consumption of tomato plants decreased dramatically with the increase of salinity. The highest yield was obtained from the control treatment in both seasons (10.6 kg m-2 in autumn, 9.1 kg m-2 in spring); however higher yield and water consumption were obtained in LF2 treatments in both growing seasons.