Abstract A crystal counter was used to determine values of ʌμτ (ʌ is the radiation yield of charge carriers, μ, microscopic mobility; τ, life time of the quasi-free charge carrier) for PE with different degrees of crystallinity and PMMA. Relations between ʌμτ and temperature were also examined for PE. It was established that the degree of crystallinity and temperature have a slight effect on the value of ʌμτ. On transition from PE to PMMA the value of ʌμτ decreases by one order of magnitude. It was shown using PS that molecular weight M υ has a slight effect on radiation electrical conductivity σ r while increasing it from 10 5 to 10 7. A correlation was derived between the variation of material density (as a result of pre-treatment and compression) and the variation of the value of σ r.