The paper presents results of multivariate analyses assessing variation in quantitative traits after the application of nitrogen and magnesium rates in cultivation of two types of maize (Zea mays L.) cultivars, i.e. ES Palazzo and the stay-green ES Paroli. The purpose of this study was to assess the multivariate phenotypic variation of 16 objects which are a combination of four nitrogen doses, two doses of magnesium and two varieties characterized by varying the rate of aging. Observations were conducted for eight traits: plant height, ear height, ear length, ear diameter, ear volume, the number of plants after emergence, the number of plants before harvest, plant loss rates in the vegetation period, observed in the course of three years (2009-2011). Statistical analysis of results was performed using the multivariate methods. Analysis of canonical variables proved to be a reliable tool providing a comprehensive assessment of variation in the effect of urea and magnesium fertilisation combinations on many traits simultaneously. The most variable treatments were A2B2C2 (50 kg N ha-1, 25 kg MgO ha-1 for ES Paroli SG) and A4B2C1 (150 kg N ha-1, 25 kg MgO ha-1 for ES Palazzo). The most similar treatments (in terms of eight traits treated jointly) included A2B2C2 (50 kg N ha-1, 25 kg MgO ha-1 for ES Paroli SG) and A3B2C2 (100 kg N ha-1, 25 kg MgO ha-1 for ES Paroli SG). Mahalanobis distances between individual treatments in individual years of observations were positive and correlated statistically significantly.