A serial thin-layer photoelectrocatalysis system was developed to study the relations between the photoelectrocatalytic activity and the structural characteristics of the mesoporous TiO2 film electrodes prepd. by an evapn.-induced self-assembly method. The structural characteristics of the mesoporous film electrodes were altered by using Pluronic F127 as the structural directing agent and by controlling the relative humidity and the temp. during coating and thermal treatment processes. Key structural characteristics of the resultant mesoporous TiO2 thin film electrodes were measured. For the mesoporous TiO2 film, the crystallinity can be introduced at a low thermal treatment temp. of 350 while at lest 450 thermal treatment temp. will be required to introduce the same degree of crystallinity to a TiO2 film prepd. via a conventional sol-gel process. The effect of key structural parameters on the photoelectrocatalytic activity was studied using glucose and succinic acid as the model org. compds. to represent weak and strong adsorbents, resp. The reported key structural properties, such as porosity, surface area and crystallinity, that affect the photocatalytic activity also critically affect the photoelectrocatalytic activity but in a different manner. This is because, for a photocatalysis application, the performance of a catalyst is mainly detd. by the characteristics of individual catalyst particles, while for a photoelectrocatalysis application the performance of a catalyst also depends on the photoelectron transport process within the photocatalyst layer this in turn relies strongly on attributes such as photocatalyst particles interconnectivity and the contact to the conducting substrate.