The electrochemical formation of TiO 2 -polyaniline (PANI) composite layers was studied by anodic polymerization of aniline in the presence of TiO 2 nanoparticles. The composite layers were investigated for their electrochemical, photoelectrochemical, and surface morphological characteristics. It was found that thick composite layers showed no photoresponse, whereas thin layers, prepared by a few potentiodynamic scans, have small photocurrents almost independent of the layer thickness. Due to the small photocurrents of the composite single-layers, bi-layered structures consisting of a first pristine PANI layer followed by an outer TiO 2 -PANI composite layer were also studied. The bi-layered structures were found to have up to threefold larger photocurrents than the composite single layers. The TiO 2 -PANI composite layers were additionally modified by deposition of platinum particles using galvanostatic electroreduction or photoreduction in the presence of hexachloroplatinate anions.