The influence of different parameters including particle size and initial total solids on the biohydrogen production from food waste was studied. The results demonstrated that the initial particle size and the concentration of initial total solids (TS0) have a positive effect on hydrogen (H-2) production. Results showed that if no pH adjustment (buffer) or particle size selection is applied, the maximal volumetric hydrogen production (2.2 L-H2 kg(-1) of the initial total solids added) was obtained at 90 gTS(0) L-1. However, the maximal total solids and chemical oxygen demand removal percentages were obtained at 10 gTS(0) L-1. For particles larger than 2 mm, the H-2 production increases as the TS0 increase. In the case of particle sizes between 0.5 and 2.0 mm, and smaller than 0.5 mm, the higher H-2 production was reached at 50 gTS(0) L-1 and 15 gTS(0) L-1, respectively. Larger particles size required more time to produce the same amount of hydrogen. The maximum hydrogen production rate per initial total solids was obtained with the smallest particle size by applying 15 gTS(0) L-1. The principal volatile fatty acids generated were acetic and butyric acids. The values of acetic acid were similar when TS0 applied between 5 to 20 g L-1 for each different particle size. Higher concentration of TS0 than 30 g L-1 results in a fast increase of acetic acid production.