The objective of the study was to determine the effect of temperature, time, and composition of dehydrating solution on the content of saccharides in fruits being dehydrated. In the experiments, hypertonic solutions containing fructooligosaccharides, saccharose, glucose, and fructose were used to osmoticly dehydrate frozen, stoned sour cherries (English Morello variety) and frozen blackcurrants (Tiben variety). Under the static conditions, dewatering was performed in different temperature ranges (25 – 60 °C) using a FOS preparation the quantity of which was four times as high as the quantity of fruit. When stirring was included in the process, sour cherries were dehydrated at 40 °C using a solution showing a varying FOS-to-saccharose ratio: 5/95, 15/85, 25/75, 50/50, and 100/0. The dehydration process of blackcurrants was performed at 40 – 80 °C and the FOS concentration was applied. It was proved that the temperature, time and the composition of the solution used significantly impacted the content of fructooligosaccharide in dried fruit. In the case of sour cherries, the best results, owing to fructooligosaccharides contained in the fruit (14.1 g/100 g) were obtained under the following conditions: temperature of 40 °C, the FOS preparation witho no saccharose added applied as an osmotic substance. In the case of blackcurrants, it was found that the best conditions were as follows: temperature: 60 °C; FOS/saccharose ratio: 100/0; process time: 120 min, hypertonic solution: FOS preparation with no saccharose added (the content of fructooligosaccharide in the product: 3.2 g/100 g).