In 2016, the Augugliaro group reported the photocatalytic effect of orthomethoxybenzaldehyde, produced by oxidation of ortho-methoxybenzyl alcohol over TiO2 photocatalysts, on homogeneous photooxidation of other alcohols under UV light. Surprisingly, this important finding that should have alarmed many researchers has been sadly neglected by the community, as this paper has received only few citations so far. Two years later, Pavan et al. addressed the question of benzyl alcohol self-oxidation under UV-light. When irradiating benzyl alcohol solution in acetonitrile with UVA light, they observed that after a long induction time benzaldehyde was formed. The same experiments performed in the presence of a TiO2 photocatalyst showed that benzaldehyde was produced immediately upon starting irradiation; however, when the TiO2 photocatalysts was extracted after a certain time interval, the benzyl alcohol oxidation clearly proceeded further and the benzaldehyde concentration continued to grow. In other words, one can assume that the formed benzaldehyde initiated a photochemical reaction with benzyl alcohol leading to the oxidation of the latter according to the mechanism adapted from Bradshaw , Heyes and Pavan and shown in Scheme 1. The current knowledge on photogeneration of radical species in benzaldehyde solutions was recently summarized in a review by Kokotos et al. It was also observed that the UV-excited benzaldehyde triplet state can be effectively quenched by tripletstate energy acceptors, and when dissolved in a good hydrogen donor it can perform hydrogen abstraction leading to the formation 𝛼-hydroxybenzyl radical in general, or of diols in the presence of alcohols. Arcas et al. provided further insight into the autooxidation processes in benzyl alcohol/benzaldehyde systems, claiming the formation of singlet oxygen being responsible for the oxidation of benzyl alcohol to benzaldehyde with concomitant production of H2O2 under UV light. However, it was not clear which species was responsible for the formation of singlet oxygen. Notably, the studies of Pavan et al. and Arcas et al. concluded that the so-called autooxidation of benzyl alcohol occurs only under UV-light and that it is completely inhibited already at 405 nm. An illustrative example that alerted our suspicion that the peculiar photochemistry of benzaldehyde might have a significant, yet unrecognized, effect on estimation of photocatalytic H2O2 production when using benzyl alcohol as electron donor can be found in a recent paper by Yamashita et al. The authors reported enhanced photocatalytic H2O2 production under visible light ( > 420 nm) using a hydrophobic Ti-based metal-organic framework (MOF) photocatalyst in a biphasic system of benzyl alcohol and water without any additional organic solvent. As the produced H2O2 was immediately extracted into the water phase and did not undergo decomposition at the photocatalyst suspended in the organic (benzyl alcohol) phase, this system allowed obtaining relatively high concentrations of H2O2.