The objective of the paper was to compare the content levels of vitamin B₁ and B₂ in frozen and sterilized canned foodstuffs made of pilei of the following mushrooms: Boletus edulis (Bull: Fr.), Pleurotus osteatus (Jacq.: Fr.) Kumm.) and Agaricus bisporus (Lange) Sing.). Prior to preservation, the pilei of mushrooms were blanched in water and water solutions of sodium metabisulfite and citric acid. Vitamins were simultaneously analyzed using an HPLC method. In the products investigated, the thiamine content ranged from 0.008 to 0.211 mg /100 g of fresh matter, and from 0.09 to 2.21 mg per 100 g dry matter, and the riboflavin content was from 0.039 to 0.252 mg, and from 0.44 to 2.87 mg, respectively. The mushroom species had the greatest effect on the different content level of vitamins in mushrooms. The content level of vitamins determined was the lowest in Pleurotus osteatus mushrooms. The highest content of thiamine was determined in Boletus edulis, and the contents of riboflavins were the highest in both the Agaricus bisporus and the Boletus edulis products. The content level of vitamin B₁ in frozen products was averagely 3.5 times higher than in the canned products, and the content of vitamin B₂ – by about 25%. When sodium metabisufite and citric acid were used for blanching, the thiamine content in the foodstuffs investigated decreased, averagely, by 33%.