Conversion of a simulated syngas containing vaporized toluene and naphthalene was studied in a non-equilibrium gliding arc plasma reformer. The reformer was designed for efficient reforming of high temperature syngas (greater than 650 degrees C) containing heavy hydrocarbons, air, and water vapor. The reactor utilized forward vortex flow, where a preheated simulated syngas containing vaporized naphthalene and toluene tar surrogate was injected tangentially in the flow to ensure effective mixing and reforming of all components. At low tar concentration (30 g/m(3)), over 90% naphthalene and toluene conversion was achieved at the benchmark specific energy input of 0.1 kWh/m(3) and energy efficiencies of 62.5 g/kWh for naphthalene and 215 g/kWh for toluene. At higher tar concentration (75 g/m(3)), over 70% naphthalene and toluene conversion was achieved at the benchmark specific energy input of 0.1 kWh/m(3) and energy efficiencies of 93.6 g/kWh for naphthalene and 369 g/kWh for toluene. Explanations for the results include effective gas mixing and plasma chemistry, such as the very fast reaction kinetics from ions, radicals and active species, specifically hydroxyl. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.