Stirred media milling is an effective method to form stable highly concentrated nanoparticle suspensions. In this work, the effect of high-energy stirred media milling on aqueous Hombikat UV100 TiO2 (Huntsman) with milling times of 0.5-96 h, containing highly concentrated suspensions with 17 wt%, was investigated. The suspensions were stabilized with nitric acid and compared with its commercial as prepared analogue Hombikat XXS100 (Huntsman). Stable and photoactive suspensions could be formed via ball milling without a loss of photoactivity between milling times of 0.5 and 2 h. To characterize the suspensions, they were freeze-dried obtaining the pure powder. It was found that the BET surface areas, the assembled structure of aggregates and agglomerates as well as particle and mesopore size distribution were decreased with increasing milling time as do the photonic efficiencies. The experimental results support the antenna mechanism theory and show that the effect of aggregates and agglomerates is highly underestimated in photocatalytic systems.