Field experiments assessed yielding, chemical composition and the selected quality parameters of starch potato tubers of Pasat, Zuzanna, Jasia, Hinga and Skawa cultivars varying with the length of vegetation period. Depending on the cultivar and the year of research, total tuber yield ranged from 19.9 to 37.8 t·ha -1, while starch yield from 3.23 to 6.68 t·ha -1. The analysed cultivars were characterized by a relatively low starch content in tubers (15.8-18.4%) and high protein concentrations (2.08-2.41%). The biggest content of these components was assessed in Skawa c.v. and the lowest in Jasia. Excessive amount of rainfall during potato vegetation unfavourably affected the amount of total and marketable yield of tubers, starch concentrations in tubers and as a result the starch yield per area unit, and mean tuber weight.