We have characterised a dye-sensitised nanoporous nanocrystalline titania film used in prototype photoelectrochemical solar cell production. The film was sensitised with two types of ruthenium (II) based dyes for different times, between 0.5 and 24 hours. The penetration and coverage for each type of dye was studied using Confocal Laser Scanning Microscopy (CLSM). Varying laser powers were applied and fluorescence images from the film have been analysed. Both dyes were found to percolate through the whole of the nanoporous film irrespective of the dyeing time but the amount of dye increased with dyeing time. The CLSM is shown to be a valuable tool for the investigation of dye penetration and coverage in porous films. (C) 2003 Kluwer Academic Publishers.