Greenhouse tomato plants (cv. Cunero F₁) were grown in the NFT units with plastic troughs filled with either rockwool or coconut fiber. The initial concentrations of sulphates in the nutrient solutions were 200, 400 or 600 mg SO₄^-2 dm^-3. The effect of different sulphate levels and type of medium on the yield, mineral composition and quality of tomato were studied. Regardless of the initial sulphate level or type of medium, the accumulation of sulphates in the nutrient solution was observed in the begining growing period. However, the organic medium (coconut fiber) cumulated more sulphates than mineral one. On the other hand, there was a higher concentration of sulphates in the recycling solution in the units with mineral (rockwool) medium compared to coconut fiber. Regardless of the type of medium the accumulation of sulphates in the root zone had no influence on the total and marketable yields as well as on the level of ascorbic acid and sugar in the fruits and its acidity. However, the yield of tomato on rockwool was higher. But the sulphate levels and type of medium did not effect the mineral composition of plants.

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