Abstract Three simple hydrocarbons: methane, ethane, and ethylene in solid state at the temperature of liquid nitrogen were studied by coincidence Doppler-broadening (CDB) spectroscopy and positron annihilation lifetime spectroscopy (PALS). Difference in the momentum distributions of σ- and π-bond electrons was observed by CDB spectroscopy. Breaking of the weak π-bonds in ethylene due to the positron irradiation and trapping of positrons by anion molecules and/or anion radicals cause inhibition in the Ps formation in ethylene observed by PALS. The breaking of the π-bonds in ethylene was detected also as a significant change in the shape of ethylene to methane CDB ratio with the elapsed experiment time.