The influence of the restricted volume of poly(styrene sulfonate)/poly(allylamine hydrochloride) capsules of different size (2.2, 4.2, and 8.1 mu m) on the TiO2-assisted photosynthesis of urea from inorganic precursors (CO2 and NO3-) in aqueous solution was demonstrated. Poly(vinyl alcohol) was employed as electron donor to facilitate the photosynthetic process. Decreasing the size of the confined microvolume of polyelectrolyte capsules accelerates the NO3-photoreduction, which is a limiting stage of the urea photosynthesis and, correspondingly, increases the efficiency of urea production. The highest yield of urea photosynthesis (37 %) was achieved for Cu-modified TiO2 nanoparticles encapsulated inside 2.2 mu m poly(styrene sulfonate)/ poly(allylamine hydrochloride) capsules.