Performance of trickle-bed and upflow reactors was studied experimentally and theoretically for an exothermic multistep hydrogenation of 1,5,9-cyclododecatriene (CDT) in n-decane as solvent over 0.5% Pd/alumina catalyst. Intrinsic kinetics was studied in a batch stirred slurry reactor using the powdered catalyst and a Langmuir-Hinshelwood type rate model is proposed. Using this rate equation, a trickle-bed-reactor model was developed which incorporates contributions of partial wetting and stagnant liquid holdup, in addition to the external and intraparticle mass transfer for the gas-phase reactant (hydrogen). It was also modified to describe the behavior of the upflow reactor. Experimental data were obtained in both upflow and downflow modes at different liquid velocities, pressures and inlet feed concentrations at 373-413 K. Reactor performance of the two modes was compared in terms of global hydrogenation rate, CDT conversion, selectivity to cyclododecene and the maximum temperature rise observed in the catalyst bed. The conversions and the global hydrogenation rate were significantly higher in a trickle- bed reactor than in the upflow reactor. Similarly, a significant temperature rise in the catalyst bed was observed for the downflow operation compared to the u-flow mode, which is explained from wetting characteristics of the catalyst bed. Model predictions for both reactors agreed well with experimental data.