Carbon nanocoil-carbon microcoil (CNC-CMC) hybrid materials were prepared via the formation of numerous carbon nanocoils (CNCs) on the surface of carbon microcoils (CMCs), using C2H2 as the source gas and CS2 as the additive gas in a thermal chemical vapor deposition system. During the reaction, CS2 was injected into the reactor in modulated on/off cycles. The density of CNCs formed on the surface of CMCs increased with an increase in the number of on/off cycle numbers. In the as-grown state, the CNC-CMC hybrid materials showed higher electrical conductivity than that of the materials composed only of CMCs. Composites of CNC-CMC hybrid materials in polyurethane (CNC-CMC@PU) and CMCs in polyurethane (CMC@PU) were fabricated. The CNC-CMC@PU composites showed higher shielding effectiveness than the CMC@PU composites, irrespective of the mixing ratios of carbon nanomaterials in PU. Based on the shielding effectiveness and electrical conductivity, we conclude that the formation of CNC-CMC hybrid materials can enhance shielding effectiveness through a reflection-based mechanism as well as an absorption-based mechanism. (C) 2017 Elsevier B.V. All rights reserved.