The chain conformation of a series of polydisperse polyesters and poly(p-phenylenes) has been investigated by means of depolarized Rayleigh scattering in solution. By considering polydisperse worm-like chains, using a Schultz-Zimm distribution, the persistence length, q, was determined from the specific depolarized Rayleigh ratio at infinite dilution and the weight average chain contour length, without involving optical anisotropies or the internal field problem. This general analysis showed that the effect of polymer nonuniformity is nearly negligible. For the polyester, q was found to be approximately 19 nm, whereas for the poly(p-phenylene) it was about 28 nm; these values exhibit the correct trend, but are higher than the corresponding ones from other techniques. Deviations are mainly attributed to the limited range of molecular weights available; this restricts the polyesters near the coil limit and the poly(p-phenylenes) near the rod Limit. Using optical anisotropy data of the monomers and Various oligomers, the validity of Flory’s addivity scheme is verified for these systems.