The requirement of fuels with ultra low impact to the environment forces the application of specific upgrading treatments to crude oils to reduce the heteroatom content, especially for N which is more difficult to be converted. Easy and well descriptive analytical methods are required to control the nature and the amount of N-containing species in petroleum cuts. GC x GC- MSD analysis proves to be a suitable technique for identifying the N-containing families, i.e. one base structure (e. g. indole) and all its derivatives with aliphatic substitutes, and quantifying (wt.%) their single components. An analytical method for identification and quantification of N-compounds, together with aromatic and S-compounds identification and distribution, was proposed and verified on crude oil fractions. (C) 2011 Elsevier Ltd. All rights reserved.