The aim of the field experiment conducted in the years 2011-2013 was to determine the content of starch, vitamin C, total protein, nitrates and glycoalkaloids in tubers of some potato cultivars (mid-early – Gawin, Legenda, Stasia, mid-late – Gustaw), taking into account the climate conditions in the years under study. An estimation was made of the effect of genotype and weather conditions during the growing season on the variation of the chemical composition of potato tubers. The investigations were carried out on a light soil (sandy loam) fertilised organically with straw and aftercrop of white mustard. Mineral fertilisation was applied in the doses of 100 kg N ha^–1, 17.5 kg P ha^–1, 99.6 kg K ha^–1. The years 2011 and 2013 were more unfavourable in terms of the weather conditions than the year 2012. The most optimal chemical composition of potato tubers, high content of nutrients and low level of anti-nutritional components was obtained in 2012. In the year 2011 significantly the lowest level of nitrates in tubers was noted. In the year 2013 significantly the highest content of nitrates and the lowest level of starch and vitamin C in tubers was observed. The highest level of starch in tubers was obtained in cultivar Gawin, vitamin C in cultivar Gustaw, and protein in cultivar Legenda. The least amount of nitrates was accumulated in the tubers of cultivar Gawin, and glycoalkaloids in cultivar Legenda. The starch content and glycoalkaloids were determined mainly by the genetic factors, the level of nitrates by the weather conditions during the growing season, and the levels of protein and vitamin C by the interaction of cultivars and years.