Tomatoes are the most commonly preserved vegetables in the world. Traditional tomato products are tomato juice, puree or ketchup but demand for dried tomatoes is increasing at the market. Drying is one of the oldest methods of preservation and often accompanies the degradation of nutritionally important ingredients. In order to protect nutrients from excessive oxidation during drying, the right choice of the drying temperature and the treatment of the raw material prior to drying are important elements of the manufacturing process. In our work we investigated the impact of various ways of antioxidant treatment of the raw material before drying on the stability of total carotenoids, polyphenols and antioxidant activity of the product. We used Uno Rosso F1 cultivar of tomatoes, dried by air at 70 °C, and the fruits were cut into slices of 3 mm thickness. To increase the stability of phytonutrients, we used the slice treatment prior to drying with 1% potassium bisulphite, ascorbic acid, citric and acetic acid and 5% sucrose and sodium chloride solutions. We found that the 1% solution of ascorbic acid was the most effective in protecting of total carotenoids and polyphenols. In the protection of total polyphenols, acetic acid and potassium bisulphite solutions were equally effective. The most significant increase in antioxidant activity was found to be ascorbic acid solution .