Nitrogen rich compounds are found in numerous planetary environments such as planetary atmospheres, meteorites and comets. To better understand the structure and composition of this natural organic material, laboratory analogs have been studied. Though HCN polymers have been studied since the beginning of the 19th century, their structure and composition are still poorly understood. In this work we report the first extended high resolution mass spectrometry study of HCN polymers. The mass spectra of the polymer contain hundreds of peaks to which we try to assign an elemental composition. Elemental analysis has been used to constrain the molecular formulae and isotopic signatures have also been used to confirm them. The large quantity of amine functions observed with both infrared (IR) spectroscopy and mass spectrometry indicates that amine groups are present in most chains found in HCN polymer. Collision induced dissociation (CID) tandem (MSn) measurements were also performed on eight molecular ions and aromatic rings have been identified.