Abstract Ion–molecule reactions have been measured for the ethane–carbon tetrafluoride mixtures of different compositions using a quadrupole mass spectrometer with a high-pressure ion source. Concentration of ethane in these mixtures ranged from 10% to 90% (at 10% increment). The following primary and secondary ions: CH 3 +, F +, C 2H 3 +, C 2H 4 +, C 2H 5 +, C 2H 6 +, C 3H 5 +, C 3H 7 +, C 4H 7 +, C 4H 9 +, C 4H 10 +, C 4H 11 + and CF 3 + were observed. Relative ion current intensities for primary and secondary ions are presented as a function both of total mixture pressure and concentration of carbon tetrafluoride in the mixture. Primary ions were produced by electrons with the energy of 300 eV. Potential of repeller electrode inside the ion source collision chamber was fixed at 5 V for all measurements. The total mixture pressure was changed from 0.7 to 26.6 Pa. Schemes of ion–molecule reactions were proposed.