The influence of addition of Zenural 70, urea and Min-A-Zel Plus on chemical composition and quality of whole maize plant silage with different degree of compression was investigated in the paper. Experiment was two-factorial (2x3) with three replications, where factor A was a degree of compression (A₁ = 680 g/dm³; A₂ = 550 g/dm³), while factor B was an additive type (Decontrol; B₂=5 g/kg urea+2 g/kg Min-A-Zel Plus; B₃=5 g/kg Zenural 70). Chemical analyses showed that with the addition of Zenural 70 and urea there was significant increase of pH value, total protein, mineral ammonia and soluble nitrogen content. The type of additive had no significant effect on production of lactic, acetic and butyric acid, while in silages with higher degree of compression (680 g/dm³) there was significantly more butyric acid. All silages were graded first class according to DLG and Flieg method, with the exception of lower compressed silage with added urea and Min-A-Zel Plus, which according to Flieg was second class. According to Zelter method, silages with added Zenural 70 were II and III class, while treatments with added urea and Min-A-Zel Plus were IV and V class.