Pump-probe experiments show that electron injection from a dye into mesoporous TiO2 is as fast as 1×1013 s-1. However, the same materials exhibit residual dye emission with lifetimes in the long nanosecond range. This inhomogeneity of e- injection rates was addressed in fluorescence lifetime microscopy experiments. The residual emission of continuous films of TiO2 was compared with that of individual anatase nanoparticles that had undergone extensive dialysis. The films produce intense emission with multiexponential decay. The mesoporous film contains physisorbed and trapped dye, which is the dominant source of the emission. The distribution of emission lifetimes may reflect the mean free paths experienced by the dye molecules diffusing within the porous TiO2. The intensity of emission from individual nanoparticles from which the loose dye was removed is orders of magnitude lower. The lifetimes are much shorter, with the primary components on subnanosecond time scale. The presence of residual emission with a ∼200 ps lifetime shows that even on dialyzed nanoparticles a fraction of dye does not inject electrons with the same rate as observed in ultrafast pump-probe experiments. It is likely that the residual emission originates from the dye bound to defects.