It is attractive to produce biohydrogen through high-rate reactors due to their ability of maintaining higher biomass concentrations by forming granules or biofilms. Here, upflow anaerobic sludge blanket (UASB) and packed bed reactor (PBR) fed with artificial wastewater were compared to study the effect of reactor configuration on hydrogen production. UASB and PBR were operated under the same conditions for 120 days at HRTs of 24-12 h and organic loading rates (OLRs) of 0.96-15.36g COD/L/d. PBR was filled with polyethylene rings, whereas UASB was amended with carbon nanotubes (CNTs) at 100 mg/L. At an OLR of 15.36 g COD/L/d, both UASB and PBR achieved maximal hydrogen production rates as 2.77 ±0.18 and 1.29 ±0.09 L/L/d, respectively, corresponding to hydrogen yields of 1.43 and 0.67 mol/mol glucose. Hydrogen contents in UASB and PBR were 47.8±0.7% and 32.6±0.7% (v/v). However, methane contents were <1% and 12.4±0.7%, respectively. The current study demonstrates that reactor configuration significantly influenced microbial activities and biohydrogen production.