This paper addresses impacts of three synthesis schemes, i.e. the direct scheme, the indirect scheme and the hybrid scheme on the economic and operational performances of hydrogen networks through a comprehensive comparative analysis. The synthesis models, flexibility analysis models and flexible design models for hydrogen networks with the three schemes are presented. The effects of different synthesis schemes on the network complexity, hydrogen consumption, total annual cost and operational flexibility of hydrogen network with single period operation and multiple period operation are studied. Results show that the direct scheme can always obtain a hydrogen network with the least connections and the highest total annual cost, whereas the other two schemes enable to generate hydrogen networks with the lower hydrogen costs and similar total annual costs. In a single period operation, the operational flexibility of the network can be improved to a certain extent, which depends strongly on the utilization efficiency of hydrogen sources and the amount of hydrogen utilities available. However, in a multiperiod operation, the hydrogen networks with indirect scheme are superior to the hydrogen networks with other two schemes in enhancing the operational flexibility due to the increases of the actual capacity redundancy and additional control variables. This work is also expected to provide a useful guidance for optimal synthesis of hydrogen networks with the desired economic and operational performances. (C) 2019 Elsevier Ltd. All rights reserved.