Aim of this study was to examine the extent to which convection drying and storage time of dehydrated mushrooms have an impact on the amount of vitamin D2. In addition, our purpose was to determine whether dried (by two different methods: hot-air and freeze drying) mushrooms can produce vitamin D2 under UVB irradiation. In order to verify the influence of UVB irradiation on the production of vitamin D2 in dehydrated mushrooms, the irradiation process of fresh sliced button mushrooms was also performed.