The temperature dependence of free-volume holes in pure poly(vinyl alcohol) (PVA) and 30% ZnCl2-treated PVA has been studied at different temperatures ranging from 25 to 150 degrees C. The dependence of the electrical conductivity on the free-volume holes is probed by the positron annihilation lifetime (PAL) technique. The lifetime tau(3) of the ortho-positronium (o-Ps) and its intensity I-3 were measured for the two samples below and above the glass transition temperatures (T-g). The observed shift in the T-g to lower value might be attributed to the increase in the electrical conductivity sigma. For treated PVA, the existence of large ionic charge carriers can be concluded from a large value of the critical hole size.