Using the pulse-radiolysis TRMC technique the mobility and lifetime of radiation-induced charge carriers is studied in poly(di-n-alkyl)silanes with pentyl, hexyl and octyl sidechains in the solid and in the mesophase. A lower limit for the sum of the mobilities of the positive and negative charge carriers in the solid phase is estimated to be of the order of 10(-5) m2V-1s-1. The mobility is found to be dependent on the silicon backbone conformation. For the all-trans conformation the mobility is a factor of two larger than for the 7/3 helix conformation. At the I-->II transition to the conformationally disordered mesophase the mobility drops an order of magnitude or more. The lifetime of the mobile charge carriers is found to increase with increasing sidechain length.