A two-step activation procedure (CO followed by synthesis gas, CO/SG) was employed prior to Fischer-Tropsch synthesis in a fixed-bed reactor using cobalt over ZnO catalyst (10 wt% Co/ZnO). The use of the CO/SG activation procedure resulted in superior performance (higher activity and lower methane selectivity) compared to one step activations with CO or H-2. High catalyst activity, in terms of CO conversion and reaction rate per unit mass of catalyst, following the CO/SG activation is attributed to the presence of hexagonal cobalt phase, which was identified from XRD measurements. Temperature programmed hydrogenation (TPH) and oxidation (TPO) were used to obtain information on the nature of cobalt phases and types of carbon on the catalyst surface after the CO activation, and after the CO/SG activation. Carbon deposited during activation of the catalyst with synthesis gas had an effect on 1-olefin content and catalytic activity. (C) 2014 Elsevier B.V. All rights reserved.