Porous layers were prepared from DEGUSSA's ITO (In2O3:Sn) nanoparticle dispersion by doctor blading followed by annealing in air. We investigated the influence of various annealing parameters on electrical, optical and morphological thin film properties. Conductance rises with increasing annealing temperature and time by more than three orders of magnitude up to 44 Omega(-1) cm(-1). Besides this we found an abrupt decrease in free charge carrier concentration above a critical annealing temperature of 250 degrees C, which leads to a step in conductance curve. In spite of particle growing during annealing no decrease in porosity was observed and in opposite to compact material, nanoparticle layers do not exhibit an appreciable shrinkage below recrystallisation temperature. These both indicate a densification hindering particle pinning effect, which is believed to be currently the main obstruction to achieve higher electrical conductivities. (c) 2007 Elsevier B.V All rights reserved.