The objective of the research undertaken was to determine the magnitude level of changes in the content of vitamin C in potato tubers after cooking and in individual technological stages of processing them to French fries, chips, and potato dices. On the basis of the research performed, it was found that the initial stages of processing potatoes, such as peeling and grinding down, caused the content of vitamin C to decrease (get lost) by 6 to 15% if compared to its content in the raw material. The magnitude level of this loss of vitamin C during the stage of cutting potatoes and rinsing them in cold water depended on their grinding degree and amounted to: 9% – in the potatoes cut to form French fries; 15% – in the potatoes cut as dices and chips. After the blanching process accomplished, higher losses of vitamin C were noted in tubers ground down to form slices and dices (33%) compared to the potatoes cut as matchsticks (27%). Comparing with the content of vitamin C in raw material, its lowest loss level was found during the stage of processing the cooked potatoes (46%) and during the stage I of frying them to make French fries (55%). The loss levels of vitamin C content were as follows: 83% during the production of chips; 85% during the stage II of making French fries; 93% during the stage of making potato dices.