A photochemical model of ion composition and electron density at heights 70-300 km in the mid-latitude, daytime ionosphere under moderate solar activity conditions has been constructed in order to reproduce electron density profiles measured by Digisonde 256 at the Dourbes Station (Jodogne 1988). The present model takes into account 38 positive and negative ions chosen on the basic of a careful analysis of photochemical processes. Much attention was paid to an analysis of production and losses of cluster-ions in the lower ionosphere. Assuming that in the quiet ionosphere the photochemical equilibrium condition is quickly established, ion and electron density profiles have been obtained from simultaneous solving of the equation system for 38 ions as well as from the equation of atmosphere neutrality. Results of calculations are in satisfactory agreement with measured electron density profiles (Jodogne 1988).