An Estonian pyrolysis shale oil has been characterized using comprehensive two dimensional gas chromatography (GC x GC) coupled to a flame ionization detector (FID) and time of flight mass spectrometer (TOF-MS). Oxygen containing compounds were abundant and the following classes were identified: benzenediols, hydroxybenzofurans, phenols, ketones, and naphthols. The large peak overlap observed for oxygenates with the hydrocarbon matrix using a non-polar x polar column combination made identification and quantification difficult. A methodology based on the more selective separation using a polar x non-polar and polar x mid polar column configurations was developed and tested. The obtained bidimensional resolution confirms that the method provides an improved separation of unsaturated hydrocarbons, mid-polar and even highly polar oxygen containing compounds. The use of an internal standard methodology allowed complete quantification of the pyrolysis shale oil both by carbon number and chemical class. (C) 2017 Elsevier B.V. All rights reserved.