Up to now, FT-IR spectroscopy remains one of the most effective techniques employed in the research of various heterogeneous processes including catalysis and photocatalysis. ere, the construction of a newly developed cell designed to conduct in situ IR spectroscopic studies of photoprocesses on powdered adsorbents in the transmission mode is presented. The capabilities of this device are illustrated by experimental data on photoinduced processes involving well known photocatalysts such as titanium dioxide. In particular, the kinetics of the UV-induced spectroscopic alterations in the IR spectrum of hydrated TiO₂ were obtained and analyzed. Moreover, the photoactivated desorption of carbon monoxide at ambient temperature from the dehydrated TiO₂ surface was observed and plausible explanations were proposed.