The aim of this study was to detect the fermentation process differences in different hybrid maize silage. We conserved in laboratory conditions hybrids of whole maize plants with different length of the vegetative period (FAO number). Maize hybrids for silage were harvested in the vegetation stage of the milk-wax maturity of corn and the content of dry matter was from 377.7 to 422.8 g.kg-1. The highest content of dry matter was typical for silages made from the hybrids with FAO number 310 (400.0 g.kg-1) and FAO 300a (400.4 g.kg-1). The content of desirable lactic acid ranged from 23.7 g.kg-1 of dry matter (FAO 350) to 58.9 g.kg-1 of dry matter (FAO 420). We detected the occurrence of undesirable butyric acid in silages from hybrids FAO 250, 300b, 310 and 380. The highest content of total alcohols we found in silages made from hybrid with FAO number 240 (25.2 g.kg-1 of dry matter). Ammonia contents were in tested silages from 0.153 (FAO 270) to 0.223 g.kg-1 of dry matter (FAO 240). The lowest value of silage titration acidity we analyzed in silage made from hybrid FAO 420 (3.66). We observed in maize silages with different length of plant maturity tested in the experiment differences in content of lactic acid, total alcohols, titration acidity, pH and content of fermentation products.