Six pure non-structural carbohydrates (glucose, fructose, sucrose, β-glucan, chicory inulin (inulin-C) and inulin of undefined source (inulin-N)) were incubated anaerobically in the inoculum prepared from rabbit caecum content and the kinetic parameters of <em>in vitro</em> gas production (total potential gas production (B), maximum fermentation rate (MFR), time when MFR was reached (TMFR), lag phase (Lag), the amount of gas (Gas8) and fermentation rate at 8 hours of incubation (FR8)) and volatile fatty acids (VFA) production after 8 hours were determined. MFRs were the greatest and TMFRs the shortest with the fermentation of sugars: glucose (MFR 36.0 ml/h; TMFR 8.6 h), fructose (MFR 38.6 ml/h; TMFR 9.6 h) and sucrose (MFR 33.2 ml/h; TMFR 9.4 h). Fermentation was the lowest in β-glucan (MFR 12.5 ml/h; TMFR 15.3 h), while fermentation of the two inulins was very different: fermentation of inulin-N was intensive and fast and similar to sugars (MFR 32.3 ml/h; TMFR 8.3 h), while inulin-C fermented slowly and with low intensity (MFR 30.5 ml/h; TMFR 11.5 h). VFA production after 8 hours of incubation was the highest for simple sugars and inulin-N, low for inulin-C, and the lowest for β-glucan (<em>p</em> &lt; 0.05). The molar proportion of acetic acid was lower in sugars and inulin-N than in inulin-C and β-glucan, which had the lowest molar proportion of butyric acid (<em>p</em> &lt; 0.05)